Index: lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiate.cpp
+++ lib/Sema/SemaTemplateInstantiate.cpp
@@ -2685,10 +2685,14 @@
         continue;
 
       if ((Context.getTargetInfo().getCXXABI().isMicrosoft() ||
-           Context.getTargetInfo().getTriple().isWindowsItaniumEnvironment()) &&
+           Context.getTargetInfo().getTriple().isWindowsItaniumEnvironment() ||
+           Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&
           TSK == TSK_ExplicitInstantiationDeclaration) {
         // In MSVC and Windows Itanium mode, explicit instantiation decl of the
         // outer class doesn't affect the inner class.
+        // In GNU mode, inner classes aren't dllexported. Don't let the
+        // instantiation cover the inner class, to avoid undefined references
+        // to inner classes that weren't exported.
         continue;
       }
 
Index: test/CodeGenCXX/mingw-template-dllexport.cpp
===================================================================
--- test/CodeGenCXX/mingw-template-dllexport.cpp
+++ test/CodeGenCXX/mingw-template-dllexport.cpp
@@ -1,5 +1,10 @@
 // RUN: %clang_cc1 -emit-llvm -triple i686-mingw32 %s -o - | FileCheck %s
 
+#define JOIN2(x, y) x##y
+#define JOIN(x, y) JOIN2(x, y)
+#define UNIQ(name) JOIN(name, __LINE__)
+#define USEMEMFUNC(class, func) void (class::*UNIQ(use)())() { return &class::func; }
+
 template <class T>
 class c {
   void f();
@@ -36,3 +41,10 @@
 
 // CHECK: define {{.*}} dllexport {{.*}} @_ZN5outerIiE1fEv
 // CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN5outerIiE5inner1fEv
+
+extern template class __declspec(dllimport) outer<char>;
+USEMEMFUNC(outer<char>, f)
+USEMEMFUNC(outer<char>::inner, f)
+
+// CHECK: declare dllimport {{.*}} @_ZN5outerIcE1fEv
+// CHECK: define {{.*}} @_ZN5outerIcE5inner1fEv