diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 6ef1ac77da3..5acd8e248d8 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -1437,6 +1437,7 @@ void MergeFunctions::replaceFunctionInTree(FnTreeType::iterator &IterToF,
   assert((F->mayBeOverridden() && G->mayBeOverridden()) ||
          (!F->mayBeOverridden() && !G->mayBeOverridden()) &&
          "Only change functions if both are strong or both are weak");
+  (void)F;
 
   IterToF->replaceBy(G);
 }