diff --git a/src/userfunc.c b/src/userfunc.c
index 0fca23a..70a3c51 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -4194,7 +4194,7 @@
 	    // In Vim9 script a function cannot have the same name as a
 	    // variable.
 	    if (vim9script && *arg == K_SPECIAL
-		     && eval_variable(name_base, STRLEN(name_base), NULL, NULL,
+		&& eval_variable(name_base, (int)STRLEN(name_base), NULL, NULL,
 			 EVAL_VAR_NOAUTOLOAD + EVAL_VAR_IMPORT
 						     + EVAL_VAR_NO_FUNC) == OK)
 	    {