diff --git a/clang/lib/Sema/SemaDeclCXX.cpp    b/clang/lib/Sema/SemaDeclCXX.cpp     
--- a/clang/lib/Sema/SemaDeclCXX.cpp   	
+++ b/clang/lib/Sema/SemaDeclCXX.cpp     	
@@ -6005,6 +6005,15 @@
       if (TSK == TSK_ImplicitInstantiation && !ClassAttr->isInherited())
         continue;

+      // If this is an MS ABI dllexport default constructor, instantiate any
+      // default arguments.
+      if (S.Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+        auto CD = dyn_cast<CXXConstructorDecl>(MD);
+        if (CD && CD->isDefaultConstructor()) {
+          S.InstantiateDefaultCtorDefaultArgs(CD);
+        }
+      }
+
       S.MarkFunctionReferenced(Class->getLocation(), MD);

       // The function will be passed to the consumer when its definition is