diff --git a/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp b/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
index 66abf7078afc..a91ee8451593 100644
--- a/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
+++ b/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
@@ -89,6 +89,7 @@ ConstantInt *CrossDSOCFI::extractBitSetTypeId(MDNode *MD) {
   // Can be null if a function was removed by an optimization.
   if (FM) {
     auto F = dyn_cast<Function>(FM->getValue());
+    (void)F;
     // But can never be a function declaration.
     assert(!F || !F->isDeclaration());
   }