diff --git a/gst/gst_private.h b/gst/gst_private.h
index ff75d2dcfe..3e68a6107e 100644
--- a/gst/gst_private.h
+++ b/gst/gst_private.h
@@ -523,7 +523,7 @@ struct _GstClockEntryImpl
   GstClockEntry entry;
   GWeakRef clock;
   GDestroyNotify destroy_entry;
-  gpointer padding[19];                 /* padding for allowing e.g. systemclock
+  gpointer padding[21];                 /* padding for allowing e.g. systemclock
                                          * to add data in lieu of overridable
                                          * virtual functions on the clock */
 };