diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index b490fa0..40e18e6 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -763,6 +763,13 @@
         !GV->isThreadLocal())
       return false;
   }
+
+  // On COFF, don't mark 'extern_weak' symbols as DSO local. If these symbols
+  // remain unresolved in the link, they can be resolved to zero, which is
+  // outside the current DSO.
+  if (TT.isOSBinFormatCOFF() && GV->hasExternalWeakLinkage())
+    return false;
+
   // Every other GV is local on COFF.
   // Make an exception for windows OS in the triple: Some firmware builds use
   // *-win32-macho triples. This (accidentally?) produced windows relocations