diff --git a/Lib/test/test_imp.py b/Lib/test/test_imp.py
index 65c9f25..bf2141f 100644
--- a/Lib/test/test_imp.py
+++ b/Lib/test/test_imp.py
@@ -217,6 +217,20 @@
         mod = imp.load_module(example, *x)
         self.assertEqual(mod.__name__, example)
 
+    def test_issue16421_multiple_modules_in_one_dll(self):
+        # Issue 16421: loading several modules from the same compiled file fails
+        m = '_testimportmultiple'
+        fileobj, pathname, description = imp.find_module(m)
+        fileobj.close()
+        mod0 = imp.load_dynamic(m, pathname)
+        mod1 = imp.load_dynamic('foo', pathname)
+        mod2 = imp.load_dynamic('bar', pathname)
+        self.assertEqual(mod0.__name__, m)
+        self.assertEqual(mod1.__name__, 'foo')
+        self.assertEqual(mod2.__name__, 'bar')
+        with self.assertRaises(ImportError):
+            imp.load_dynamic('nonexistent', pathname)
+
     def test_load_dynamic_ImportError_path(self):
         # Issue #1559549 added `name` and `path` attributes to ImportError
         # in order to provide better detail. Issue #10854 implemented those
diff --git a/Misc/ACKS b/Misc/ACKS
index e7b2d46..bb96fab 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1109,6 +1109,7 @@
 J. Sipprell
 Kragen Sitaker
 Michael Sloan
+Václav Šmilauer
 Christopher Smith
 Eric V. Smith
 Gregory P. Smith
diff --git a/Misc/NEWS b/Misc/NEWS
index 91fc7c0..f04a08e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@
 Core and Builtins
 -----------------
 
+- Issue #16421: loading multiple modules from one shared object is now
+  handled correctly (previously, the first module loaded from that file
+  was silently returned). Patch by Václav Šmilauer.
+
 - Issue #16602: When a weakref's target was part of a long deallocation
   chain, the object could remain reachable through its weakref even though
   its refcount had dropped to zero.
diff --git a/Modules/_testimportmultiple.c b/Modules/_testimportmultiple.c
new file mode 100644
index 0000000..baad29d
--- /dev/null
+++ b/Modules/_testimportmultiple.c
@@ -0,0 +1,57 @@
+/*
+ * C extensions module to test importing multiple modules from one compiled
+ * file (issue16421). This file defines 3 modules (_testimportmodule,
+ * foo, bar), only the first one is called the same as the compiled file.
+ */
+#include<Python.h>
+
+static struct PyModuleDef _testimportmultiple = {
+    PyModuleDef_HEAD_INIT,
+    "_testimportmultiple",
+    "_testimportmultiple doc",
+    -1,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL
+};
+
+PyMODINIT_FUNC PyInit__testimportmultiple()
+{
+    return PyModule_Create(&_testimportmultiple);
+}
+
+static struct PyModuleDef _foomodule = {
+    PyModuleDef_HEAD_INIT,
+    "foo",
+    "foo doc",
+    -1,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL
+};
+
+PyMODINIT_FUNC PyInit_foo()
+{
+    return PyModule_Create(&_foomodule);
+}
+
+static struct PyModuleDef _barmodule = {
+    PyModuleDef_HEAD_INIT,
+    "bar",
+    "bar doc",
+    -1,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL
+};
+
+PyMODINIT_FUNC PyInit_bar(){
+    return PyModule_Create(&_barmodule);
+}
+
diff --git a/PC/VS9.0/_testimportmultiple.vcproj b/PC/VS9.0/_testimportmultiple.vcproj
new file mode 100644
index 0000000..14d910d
--- /dev/null
+++ b/PC/VS9.0/_testimportmultiple.vcproj
@@ -0,0 +1,521 @@
+<?xml version="1.0" encoding="Windows-1252"?>
+<VisualStudioProject
+	ProjectType="Visual C++"
+	Version="9.00"
+	Name="_testimportmultiple"
+	ProjectGUID="{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}"
+	RootNamespace="_testimportmultiple"
+	Keyword="Win32Proj"
+	TargetFrameworkVersion="196613"
+	>
+	<Platforms>
+		<Platform
+			Name="Win32"
+		/>
+		<Platform
+			Name="x64"
+		/>
+	</Platforms>
+	<ToolFiles>
+	</ToolFiles>
+	<Configurations>
+		<Configuration
+			Name="Debug|Win32"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd_d.vsprops"
+			CharacterSet="0"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="Debug|x64"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd_d.vsprops;.\x64.vsprops"
+			CharacterSet="0"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+				TargetEnvironment="3"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="Release|Win32"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="Release|x64"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops;.\x64.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+				TargetEnvironment="3"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="PGInstrument|Win32"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops;.\pginstrument.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="PGInstrument|x64"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops;.\x64.vsprops;.\pginstrument.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+				TargetEnvironment="3"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+				TargetMachine="17"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="PGUpdate|Win32"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops;.\pgupdate.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+		<Configuration
+			Name="PGUpdate|x64"
+			ConfigurationType="2"
+			InheritedPropertySheets=".\pyd.vsprops;.\x64.vsprops;.\pgupdate.vsprops"
+			CharacterSet="0"
+			WholeProgramOptimization="1"
+			>
+			<Tool
+				Name="VCPreBuildEventTool"
+			/>
+			<Tool
+				Name="VCCustomBuildTool"
+			/>
+			<Tool
+				Name="VCXMLDataGeneratorTool"
+			/>
+			<Tool
+				Name="VCWebServiceProxyGeneratorTool"
+			/>
+			<Tool
+				Name="VCMIDLTool"
+				TargetEnvironment="3"
+			/>
+			<Tool
+				Name="VCCLCompilerTool"
+			/>
+			<Tool
+				Name="VCManagedResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCResourceCompilerTool"
+			/>
+			<Tool
+				Name="VCPreLinkEventTool"
+			/>
+			<Tool
+				Name="VCLinkerTool"
+				BaseAddress="0x1e1F0000"
+				TargetMachine="17"
+			/>
+			<Tool
+				Name="VCALinkTool"
+			/>
+			<Tool
+				Name="VCManifestTool"
+			/>
+			<Tool
+				Name="VCXDCMakeTool"
+			/>
+			<Tool
+				Name="VCBscMakeTool"
+			/>
+			<Tool
+				Name="VCFxCopTool"
+			/>
+			<Tool
+				Name="VCAppVerifierTool"
+			/>
+			<Tool
+				Name="VCPostBuildEventTool"
+			/>
+		</Configuration>
+	</Configurations>
+	<References>
+	</References>
+	<Files>
+		<Filter
+			Name="Source Files"
+			>
+			<File
+				RelativePath="..\..\Modules\_testimportmultiple.c"
+				>
+			</File>
+		</Filter>
+	</Files>
+	<Globals>
+	</Globals>
+</VisualStudioProject>
diff --git a/PC/VS9.0/pcbuild.sln b/PC/VS9.0/pcbuild.sln
index 94cd4b5..9956e46 100644
--- a/PC/VS9.0/pcbuild.sln
+++ b/PC/VS9.0/pcbuild.sln
@@ -87,6 +87,11 @@
 		{CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26} = {CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26}
 	EndProjectSection
 EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_testimportmultiple", "_testimportmultiple.vcproj", "{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}"
+	ProjectSection(ProjectDependencies) = postProject
+		{CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26} = {CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26}
+	EndProjectSection
+EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_tkinter", "_tkinter.vcproj", "{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}"
 	ProjectSection(ProjectDependencies) = postProject
 		{CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26} = {CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26}
@@ -422,6 +427,22 @@
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|Win32.Build.0 = Release|Win32
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|x64.ActiveCfg = Release|x64
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|x64.Build.0 = Release|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|Win32.ActiveCfg = Debug|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|Win32.Build.0 = Debug|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|x64.ActiveCfg = Debug|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|x64.Build.0 = Debug|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|Win32.ActiveCfg = PGInstrument|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|Win32.Build.0 = PGInstrument|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|x64.ActiveCfg = PGInstrument|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|x64.Build.0 = PGInstrument|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|Win32.ActiveCfg = PGUpdate|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|Win32.Build.0 = PGUpdate|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|x64.ActiveCfg = PGUpdate|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|x64.Build.0 = PGUpdate|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|Win32.ActiveCfg = Release|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|Win32.Build.0 = Release|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|x64.ActiveCfg = Release|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|x64.Build.0 = Release|x64
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|Win32.ActiveCfg = Debug|Win32
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|Win32.Build.0 = Debug|Win32
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|x64.ActiveCfg = Debug|x64
diff --git a/PCbuild/_testimportmultiple.vcxproj b/PCbuild/_testimportmultiple.vcxproj
new file mode 100644
index 0000000..84984ff
--- /dev/null
+++ b/PCbuild/_testimportmultiple.vcxproj
@@ -0,0 +1,218 @@
+﻿<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|Win32">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|x64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|Win32">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|x64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}</ProjectGuid>
+    <RootNamespace>_testimportmultiple</RootNamespace>
+    <Keyword>Win32Proj</Keyword>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+    <Import Project="pgupdate.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+    <Import Project="pginstrument.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd_d.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+    <Import Project="x64.props" />
+    <Import Project="pgupdate.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+    <Import Project="x64.props" />
+    <Import Project="pginstrument.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd.props" />
+    <Import Project="x64.props" />
+  </ImportGroup>
+  <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyd_d.props" />
+    <Import Project="x64.props" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <_ProjectFileVersion>10.0.30319.1</_ProjectFileVersion>
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" />
+    <CodeAnalysisRuleSet Condition="'$(Configuration)|$(Platform)'=='Release|x64'">AllRules.ruleset</CodeAnalysisRuleSet>
+    <CodeAnalysisRules Condition="'$(Configuration)|$(Platform)'=='Release|x64'" />
+    <CodeAnalysisRuleAssemblies Condition="'$(Configuration)|$(Platform)'=='Release|x64'" />
+  </PropertyGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|Win32'">
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='PGInstrument|x64'">
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+      <TargetMachine>MachineX64</TargetMachine>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|Win32'">
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='PGUpdate|x64'">
+    <Midl>
+      <TargetEnvironment>X64</TargetEnvironment>
+    </Midl>
+    <Link>
+      <BaseAddress>0x1e1F0000</BaseAddress>
+      <TargetMachine>MachineX64</TargetMachine>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <ClCompile Include="..\Modules\_testimportmultiple.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="pythoncore.vcxproj">
+      <Project>{cf7ac3d1-e2df-41d2-bea6-1e2556cdea26}</Project>
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>
diff --git a/PCbuild/_testimportmultiple.vcxproj.filters b/PCbuild/_testimportmultiple.vcxproj.filters
new file mode 100644
index 0000000..db0d0a6
--- /dev/null
+++ b/PCbuild/_testimportmultiple.vcxproj.filters
@@ -0,0 +1,13 @@
+﻿<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <Filter Include="Source Files">
+      <UniqueIdentifier>{1ec38ad9-1abf-4b80-8628-ac43ccba324b}</UniqueIdentifier>
+    </Filter>
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="..\Modules\_testimportmultiple.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+</Project>
diff --git a/PCbuild/pcbuild.sln b/PCbuild/pcbuild.sln
index 0edcdf6..e5ba1de 100644
--- a/PCbuild/pcbuild.sln
+++ b/PCbuild/pcbuild.sln
@@ -38,6 +38,8 @@
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_testcapi", "_testcapi.vcxproj", "{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}"
 EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_testimportmultiple", "_testimportmultiple.vcxproj", "{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}"
+EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_tkinter", "_tkinter.vcxproj", "{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}"
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_bz2", "_bz2.vcxproj", "{73FCD2BD-F133-46B7-8EC1-144CD82A59D5}"
@@ -344,6 +346,22 @@
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|Win32.Build.0 = Release|Win32
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|x64.ActiveCfg = Release|x64
 		{6901D91C-6E48-4BB7-9FEC-700C8131DF1D}.Release|x64.Build.0 = Release|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|Win32.ActiveCfg = Debug|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|Win32.Build.0 = Debug|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|x64.ActiveCfg = Debug|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Debug|x64.Build.0 = Debug|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|Win32.ActiveCfg = PGInstrument|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|Win32.Build.0 = PGInstrument|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|x64.ActiveCfg = PGInstrument|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGInstrument|x64.Build.0 = PGInstrument|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|Win32.ActiveCfg = PGUpdate|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|Win32.Build.0 = PGUpdate|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|x64.ActiveCfg = PGUpdate|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.PGUpdate|x64.Build.0 = PGUpdate|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|Win32.ActiveCfg = Release|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|Win32.Build.0 = Release|Win32
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|x64.ActiveCfg = Release|x64
+		{36D0C52C-DF4E-45D0-8BC7-E294C3ABC781}.Release|x64.Build.0 = Release|x64
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|Win32.ActiveCfg = Debug|Win32
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|Win32.Build.0 = Debug|Win32
 		{4946ECAC-2E69-4BF8-A90A-F5136F5094DF}.Debug|x64.ActiveCfg = Debug|x64
diff --git a/Python/import.c b/Python/import.c
index 6882b57..8e7482a 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -452,12 +452,12 @@
 
 /* Magic for extension modules (built-in as well as dynamically
    loaded).  To prevent initializing an extension module more than
-   once, we keep a static dictionary 'extensions' keyed by module name
-   (for built-in modules) or by filename (for dynamically loaded
-   modules), containing these modules.  A copy of the module's
-   dictionary is stored by calling _PyImport_FixupExtensionObject()
-   immediately after the module initialization function succeeds.  A
-   copy can be retrieved from there by calling
+   once, we keep a static dictionary 'extensions' keyed by the tuple
+   (module name, module name)  (for built-in modules) or by
+   (filename, module name) (for dynamically loaded modules), containing these
+   modules.  A copy of the module's dictionary is stored by calling
+   _PyImport_FixupExtensionObject() immediately after the module initialization
+   function succeeds.  A copy can be retrieved from there by calling
    _PyImport_FindExtensionObject().
 
    Modules which do support multiple initialization set their m_size
@@ -470,7 +470,7 @@
 _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
                                PyObject *filename)
 {
-    PyObject *modules, *dict;
+    PyObject *modules, *dict, *filename_name;
     struct PyModuleDef *def;
     if (extensions == NULL) {
         extensions = PyDict_New();
@@ -508,7 +508,11 @@
         if (def->m_base.m_copy == NULL)
             return -1;
     }
-    PyDict_SetItem(extensions, filename, (PyObject*)def);
+    filename_name = PyTuple_Pack(2,filename, name);
+    if (filename_name == NULL)
+        return -1;
+    if (PyDict_SetItem(extensions, filename_name, (PyObject*)def) < 0)
+        return -1;
     return 0;
 }
 
@@ -528,11 +532,14 @@
 PyObject *
 _PyImport_FindExtensionObject(PyObject *name, PyObject *filename)
 {
-    PyObject *mod, *mdict;
+    PyObject *mod, *mdict, *filename_name;
     PyModuleDef* def;
     if (extensions == NULL)
         return NULL;
-    def = (PyModuleDef*)PyDict_GetItem(extensions, filename);
+    filename_name = PyTuple_Pack(2,filename, name);
+    if (filename_name == NULL)
+        return NULL;
+    def = (PyModuleDef*)PyDict_GetItem(extensions, filename_name);
     if (def == NULL)
         return NULL;
     if (def->m_size == -1) {
diff --git a/Tools/msi/msi.py b/Tools/msi/msi.py
index f9b477f..cd1c60b 100644
--- a/Tools/msi/msi.py
+++ b/Tools/msi/msi.py
@@ -101,6 +101,7 @@
     '_decimal.pyd',
     '_testbuffer.pyd',
     '_sha3.pyd',
+    '_testimportmultiple.pyd',
 ]
 
 # Well-known component UUIDs
diff --git a/setup.py b/setup.py
index c46a2ff..0eca3ec 100644
--- a/setup.py
+++ b/setup.py
@@ -594,6 +594,8 @@
                                depends=['testcapi_long.h']) )
         # Python PEP-3118 (buffer protocol) test module
         exts.append( Extension('_testbuffer', ['_testbuffer.c']) )
+        # Test loading multiple modules from one compiled file (http://bugs.python.org/issue16421)
+        exts.append( Extension('_testimportmultiple', ['_testimportmultiple.c']) )
         # profiler (_lsprof is for cProfile.py)
         exts.append( Extension('_lsprof', ['_lsprof.c', 'rotatingtree.c']) )
         # static Unicode character database