diff --git a/clang/lib/AST/Interp/InterpBuiltin.cpp b/clang/lib/AST/Interp/InterpBuiltin.cpp
index 4ba518e5f0619..371240065179e 100644
--- a/clang/lib/AST/Interp/InterpBuiltin.cpp
+++ b/clang/lib/AST/Interp/InterpBuiltin.cpp
@@ -1207,6 +1207,10 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
     break;
 
   default:
+    S.FFDiag(S.Current->getLocation(OpPC),
+             diag::note_invalid_subexpr_in_const_expr)
+        << S.Current->getRange(OpPC);
+
     return false;
   }