diff --git a/xC.c b/xC.c
index 9664cb7..5b8dda2 100644
--- a/xC.c
+++ b/xC.c
@@ -4622,11 +4622,24 @@ irc_make_buffer_name (struct server *s, const char *target)
 	if (!target)
 		return xstrdup (s->name);
 
-	// XXX: this may be able to trigger the uniqueness assertion with non-UTF-8
 	char *target_utf8 = irc_to_utf8 (target);
-	char *result = xstrdup_printf ("%s.%s", s->name, target_utf8);
+	char *name = xstrdup_printf ("%s.%s", s->name, target_utf8);
 	free (target_utf8);
-	return result;
+
+	struct buffer *conflict = buffer_by_name (s->ctx, name);
+	if (!conflict)
+		return name;
+
+	hard_assert (conflict->server == s);
+
+	// Fix up any conflicts.  Note that while parentheses aren't allowed
+	// in IRC nicknames, they may occur in channel names.
+	int i = 0;
+	char *unique = xstrdup_printf ("%s(%d)", name, ++i);
+	while (buffer_by_name (s->ctx, unique))
+		cstr_set (&unique, xstrdup_printf ("%s(%d)", name, ++i));
+	free (name);
+	return unique;
 }
 
 static void