diff --git a/glib/gtimezone.c b/glib/gtimezone.c
index 72a4916ad..b3220dc35 100644
--- a/glib/gtimezone.c
+++ b/glib/gtimezone.c
@@ -1677,7 +1677,10 @@ interval_end (GTimeZone *tz,
               guint      interval)
 {
   if (tz->transitions && interval < tz->transitions->len)
-    return (TRANSITION(interval)).time - 1;
+    {
+      gint64 lim = (TRANSITION(interval)).time;
+      return lim - (lim != G_MININT64);
+    }
   return G_MAXINT64;
 }