diff --git a/stage1/wasm.h b/stage1/wasm.h
index 276d340bbb..277f865563 100644
--- a/stage1/wasm.h
+++ b/stage1/wasm.h
@@ -52,6 +52,7 @@ static const char *WasmMut_toC(enum WasmMut val_type) {
         case WasmMut_var: return "";
         default: panic("unsupported mut");
     }
+    return NULL;
 }
 
 enum WasmOpcode {