Index: lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiate.cpp	(revision 145552)
+++ lib/Sema/SemaTemplateInstantiate.cpp	(working copy)
@@ -1683,6 +1683,10 @@
                        TemplateSpecializationKind TSK,
                        bool Complain) {
   bool Invalid = false;
+    
+  RequireCompleteType(Pattern->getLocation(), 
+                      QualType(Pattern->getTypeForDecl(), 0), 
+                      diag::err_incomplete_type);
 
   CXXRecordDecl *PatternDef
     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());