diff --git a/notmuch-reply.c b/notmuch-reply.c
index 31e2c87c..e4de4743 100644
--- a/notmuch-reply.c
+++ b/notmuch-reply.c
@@ -78,7 +78,7 @@ address_is_users (const char *address, notmuch_config_t *config)
 {
     const char *primary;
     char **other;
-    unsigned int i, other_len;
+    size_t i, other_len;
 
     primary = notmuch_config_get_user_primary_email (config);
     if (strcmp (primary, address) == 0)