diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 1288568..42d7d2b 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1605,8 +1605,18 @@
   if (previous.empty())
     return;
 
-  // If this declaration has external
-  bool hasExternalLinkage = decl->hasExternalLinkage();
+  // If this declaration would have external linkage if it were the first
+  // declaration of this name, then it may in fact be a redeclaration of
+  // some hidden declaration, so include those too. We don't need to worry
+  // about some previous visible declaration giving this declaration external
+  // linkage, because in that case, we'll mark this declaration as a redecl
+  // of the visible decl, and that decl will already be a redecl of the
+  // hidden declaration if that's appropriate.
+  //
+  // Don't cache this linkage computation, because it's not yet correct: we
+  // may later give this declaration a previous declaration which changes
+  // its linkage.
+  bool hasExternalLinkage = decl->hasExternalLinkageUncached();
 
   LookupResult::Filter filter = previous.makeFilter();
   while (filter.hasNext()) {