diff --git a/src/eval.c b/src/eval.c
index a45b71d..7d28e71 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -19195,11 +19195,21 @@
 		    goto theend;	/* type error; errmsg already given */
 		if (i == 1)
 		    info.item_compare_ic = TRUE;
-		else
+		else if (argvars[1].v_type != VAR_NUMBER)
 		    info.item_compare_func = get_tv_string(&argvars[1]);
+		else if (i != 0)
+		{
+		    EMSG(_(e_invarg));
+		    goto theend;
+		}
 		if (info.item_compare_func != NULL)
 		{
-		    if (STRCMP(info.item_compare_func, "n") == 0)
+		    if (*info.item_compare_func == NUL)
+		    {
+			/* empty string means default sort */
+			info.item_compare_func = NULL;
+		    }
+		    else if (STRCMP(info.item_compare_func, "n") == 0)
 		    {
 			info.item_compare_func = NULL;
 			info.item_compare_numeric = TRUE;