diff --git a/mailmap.c b/mailmap.c
index 81890a6680..9e9589730f 100644
--- a/mailmap.c
+++ b/mailmap.c
@@ -71,22 +71,17 @@ static void add_mapping(struct string_list *map,
 			char *old_name, char *old_email)
 {
 	struct mailmap_entry *me;
-	int index;
+	struct string_list_item *item;
 
 	if (old_email == NULL) {
 		old_email = new_email;
 		new_email = NULL;
 	}
 
-	if ((index = string_list_find_insert_index(map, old_email, 1)) < 0) {
-		/* mailmap entry exists, invert index value */
-		index = -1 - index;
-		me = (struct mailmap_entry *)map->items[index].util;
+	item = string_list_insert(map, old_email);
+	if (item->util) {
+		me = (struct mailmap_entry *)item->util;
 	} else {
-		/* create mailmap entry */
-		struct string_list_item *item;
-
-		item = string_list_insert_at_index(map, index, old_email);
 		me = xcalloc(1, sizeof(struct mailmap_entry));
 		me->namemap.strdup_strings = 1;
 		me->namemap.cmp = namemap_cmp;
@@ -94,8 +89,8 @@ static void add_mapping(struct string_list *map,
 	}
 
 	if (old_name == NULL) {
-		debug_mm("mailmap: adding (simple) entry for %s at index %d\n",
-			 old_email, index);
+		debug_mm("mailmap: adding (simple) entry for '%s'\n", old_email);
+
 		/* Replace current name and new email for simple entry */
 		if (new_name) {
 			free(me->name);
@@ -107,8 +102,7 @@ static void add_mapping(struct string_list *map,
 		}
 	} else {
 		struct mailmap_info *mi = xcalloc(1, sizeof(struct mailmap_info));
-		debug_mm("mailmap: adding (complex) entry for %s at index %d\n",
-			 old_email, index);
+		debug_mm("mailmap: adding (complex) entry for '%s'\n", old_email);
 		if (new_name)
 			mi->name = xstrdup(new_name);
 		if (new_email)