diff --git a/src/if_cscope.c b/src/if_cscope.c
index 815db55..4e313ce 100644
--- a/src/if_cscope.c
+++ b/src/if_cscope.c
@@ -2496,6 +2496,14 @@
     char_u	*prepend = NULL;
     char_u	buf[NUMBUFLEN];
 
+    if (in_vim9script()
+	    && (check_for_opt_number_arg(argvars, 0) == FAIL
+		|| (argvars[0].v_type != VAR_UNKNOWN
+		    && (check_for_opt_string_arg(argvars, 1) == FAIL
+			|| (argvars[1].v_type != VAR_UNKNOWN
+			    && check_for_opt_string_arg(argvars, 2) == FAIL)))))
+	return;
+
     if (argvars[0].v_type != VAR_UNKNOWN
 	    && argvars[1].v_type != VAR_UNKNOWN)
     {