diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 2bb975943c..c1ffbd89b8 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -3656,9 +3656,14 @@ static void
 CallXactCallbacks(XactEvent event)
 {
 	XactCallbackItem *item;
+	XactCallbackItem *next;
 
-	for (item = Xact_callbacks; item; item = item->next)
+	for (item = Xact_callbacks; item; item = next)
+	{
+		/* allow callbacks to unregister themselves when called */
+		next = item->next;
 		item->callback(event, item->arg);
+	}
 }
 
 
@@ -3713,9 +3718,14 @@ CallSubXactCallbacks(SubXactEvent event,
 					 SubTransactionId parentSubid)
 {
 	SubXactCallbackItem *item;
+	SubXactCallbackItem *next;
 
-	for (item = SubXact_callbacks; item; item = item->next)
+	for (item = SubXact_callbacks; item; item = next)
+	{
+		/* allow callbacks to unregister themselves when called */
+		next = item->next;
 		item->callback(event, mySubid, parentSubid, item->arg);
+	}
 }
 
 
diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c
index ece5d98261..37b43ee1f8 100644
--- a/src/backend/utils/resowner/resowner.c
+++ b/src/backend/utils/resowner/resowner.c
@@ -501,6 +501,7 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 	ResourceOwner child;
 	ResourceOwner save;
 	ResourceReleaseCallbackItem *item;
+	ResourceReleaseCallbackItem *next;
 	Datum		foundres;
 
 	/* Recurse to handle descendants */
@@ -701,8 +702,12 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 	}
 
 	/* Let add-on modules get a chance too */
-	for (item = ResourceRelease_callbacks; item; item = item->next)
+	for (item = ResourceRelease_callbacks; item; item = next)
+	{
+		/* allow callbacks to unregister themselves when called */
+		next = item->next;
 		item->callback(phase, isCommit, isTopLevel, item->arg);
+	}
 
 	CurrentResourceOwner = save;
 }