diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 970b2ec..46cd285 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7885,7 +7885,7 @@
       (MD->getTypeQualifiers() & Qualifiers::Const) == 0) {
     CXXMethodDecl *OldMD = nullptr;
     if (OldDecl)
-      OldMD = dyn_cast<CXXMethodDecl>(OldDecl->getAsFunction());
+      OldMD = dyn_cast_or_null<CXXMethodDecl>(OldDecl->getAsFunction());
     if (!OldMD || !OldMD->isStatic()) {
       const FunctionProtoType *FPT =
         MD->getType()->castAs<FunctionProtoType>();