diff --git a/src/filepath.c b/src/filepath.c
index 75662b4..e81eeb1 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -788,9 +788,13 @@
     rettv->vval.v_string = NULL;
 
     if (argvars[0].v_type != VAR_STRING)
+    {
 	// Returning an empty string means it failed.
 	// No error message, for historic reasons.
+	if (in_vim9script())
+	    (void) check_for_string_arg(argvars, 0);
 	return;
+    }
 
     // Return the current directory
     cwd = alloc(MAXPATHL);