diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index abe912f..6fee23a 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3771,6 +3771,8 @@
   if (PatternDef) {
     Pattern = PatternDef->getBody(PatternDef);
     PatternDecl = PatternDef;
+    if (PatternDef->willHaveBody())
+      PatternDef = nullptr;
   }
 
   // FIXME: We need to track the instantiation stack in order to know which