diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -86,7 +86,7 @@
                                      LLVMDiagnosticHandler Handler,
                                      void *DiagnosticContext) {
   unwrap(C)->setDiagnosticHandlerCallBack(
-      LLVM_EXTENSION reinterpret_cast<DiagnosticHandler::DiagnosticHandlerTy>(
+      LLVM_EXTENSION reinterpret_cast<DiagnosticHandler::DiagnosticHandlerTy &>(
           Handler),
       DiagnosticContext);
 }