diff --git a/include/clang/Lex/PPCallbacks.h b/include/clang/Lex/PPCallbacks.h
index 99fe29b..782f2d5 100644
--- a/include/clang/Lex/PPCallbacks.h
+++ b/include/clang/Lex/PPCallbacks.h
@@ -89,7 +89,8 @@
 
   /// MacroUndefined - This hook is called whenever a macro #undef is seen.
   /// MI is released immediately following this callback.
-  virtual void MacroUndefined(const IdentifierInfo *II, const MacroInfo *MI) {
+  virtual void MacroUndefined(SourceLocation Loc, const IdentifierInfo *II,
+                              const MacroInfo *MI) {
   }
 };
 
@@ -149,9 +150,10 @@
     Second->MacroDefined(II, MI);
   }
 
-  virtual void MacroUndefined(const IdentifierInfo *II, const MacroInfo *MI) {
-    First->MacroUndefined(II, MI);
-    Second->MacroUndefined(II, MI);
+  virtual void MacroUndefined(SourceLocation Loc, const IdentifierInfo *II,
+                              const MacroInfo *MI) {
+    First->MacroUndefined(Loc, II, MI);
+    Second->MacroUndefined(Loc, II, MI);
   }
 };
 
diff --git a/include/clang/Lex/PreprocessingRecord.h b/include/clang/Lex/PreprocessingRecord.h
index ef28af9..730f04f 100644
--- a/include/clang/Lex/PreprocessingRecord.h
+++ b/include/clang/Lex/PreprocessingRecord.h
@@ -257,7 +257,8 @@
     
     virtual void MacroExpands(const Token &Id, const MacroInfo* MI);
     virtual void MacroDefined(const IdentifierInfo *II, const MacroInfo *MI);
-    virtual void MacroUndefined(const IdentifierInfo *II, const MacroInfo *MI);
+    virtual void MacroUndefined(SourceLocation Loc, const IdentifierInfo *II,
+                                const MacroInfo *MI);
   };
 } // end namespace clang
 
diff --git a/lib/Frontend/PrintPreprocessedOutput.cpp b/lib/Frontend/PrintPreprocessedOutput.cpp
index 73bca9a..e68fd58 100644
--- a/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -137,6 +137,9 @@
   /// MacroDefined - This hook is called whenever a macro definition is seen.
   void MacroDefined(const IdentifierInfo *II, const MacroInfo *MI);
 
+  /// MacroUndefined - This hook is called whenever a macro #undef is seen.
+  void MacroUndefined(SourceLocation Loc, const IdentifierInfo *II,
+                      const MacroInfo *MI);
 };
 }  // end anonymous namespace
 
@@ -280,6 +283,16 @@
   EmittedMacroOnThisLine = true;
 }
 
+void PrintPPOutputPPCallbacks::MacroUndefined(SourceLocation Loc,
+                                              const IdentifierInfo *II,
+                                              const MacroInfo *MI) {
+  // Only print out macro definitions in -dD mode.
+  if (!DumpDefines) return;
+
+  MoveToLine(Loc);
+  OS << "#undef " << II->getName();
+  EmittedMacroOnThisLine = true;
+}
 
 void PrintPPOutputPPCallbacks::PragmaComment(SourceLocation Loc,
                                              const IdentifierInfo *Kind,
diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index 15ab049..53619f9 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -1508,7 +1508,8 @@
 
   // If the callbacks want to know, tell them about the macro #undef.
   if (Callbacks)
-    Callbacks->MacroUndefined(MacroNameTok.getIdentifierInfo(), MI);
+    Callbacks->MacroUndefined(MacroNameTok.getLocation(),
+                              MacroNameTok.getIdentifierInfo(), MI);
 
   // Free macro definition.
   ReleaseMacroInfo(MI);
diff --git a/lib/Lex/PreprocessingRecord.cpp b/lib/Lex/PreprocessingRecord.cpp
index 6966c38..c446d96 100644
--- a/lib/Lex/PreprocessingRecord.cpp
+++ b/lib/Lex/PreprocessingRecord.cpp
@@ -118,7 +118,8 @@
   PreprocessedEntities.push_back(Def);
 }
 
-void PreprocessingRecord::MacroUndefined(const IdentifierInfo *II, 
+void PreprocessingRecord::MacroUndefined(SourceLocation Loc,
+                                         const IdentifierInfo *II,
                                          const MacroInfo *MI) {
   llvm::DenseMap<const MacroInfo *, MacroDefinition *>::iterator Pos
     = MacroDefinitions.find(MI);
diff --git a/test/Preprocessor/dump-macros-undef.c b/test/Preprocessor/dump-macros-undef.c
new file mode 100644
index 0000000..358fd17
--- /dev/null
+++ b/test/Preprocessor/dump-macros-undef.c
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -E -dD %s | FileCheck %s
+// PR7818
+
+// CHECK: # 1 "{{.+}}.c"
+#define X 3
+// CHECK: #define X 3
+#undef X
+// CHECK: #undef X