diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 5016181fd7..9fb68cd7b3 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8047,7 +8047,7 @@ heap_xlog_cleanup_info(XLogReaderState *record)
 }
 
 /*
- * Handles HEAP2_CLEAN record type
+ * Handles XLOG_HEAP2_CLEAN record type
  */
 static void
 heap_xlog_clean(XLogReaderState *record)
@@ -8055,7 +8055,6 @@ heap_xlog_clean(XLogReaderState *record)
 	XLogRecPtr	lsn = record->EndRecPtr;
 	xl_heap_clean *xlrec = (xl_heap_clean *) XLogRecGetData(record);
 	Buffer		buffer;
-	Size		freespace = 0;
 	RelFileNode rnode;
 	BlockNumber blkno;
 	XLogRedoAction action;
@@ -8107,8 +8106,6 @@ heap_xlog_clean(XLogReaderState *record)
 								nowdead, ndead,
 								nowunused, nunused);
 
-		freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
-
 		/*
 		 * Note: we don't worry about updating the page's prunability hints.
 		 * At worst this will cause an extra prune cycle to occur soon.
@@ -8117,18 +8114,24 @@ heap_xlog_clean(XLogReaderState *record)
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(buffer);
 	}
+
 	if (BufferIsValid(buffer))
+	{
+		Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
+
 		UnlockReleaseBuffer(buffer);
 
-	/*
-	 * Update the FSM as well.
-	 *
-	 * XXX: Don't do this if the page was restored from full page image. We
-	 * don't bother to update the FSM in that case, it doesn't need to be
-	 * totally accurate anyway.
-	 */
-	if (action == BLK_NEEDS_REDO)
+		/*
+		 * After cleaning records from a page, it's useful to update the FSM
+		 * about it, as it may cause the page become target for insertions
+		 * later even if vacuum decides not to visit it (which is possible if
+		 * gets marked all-visible.)
+		 *
+		 * Do this regardless of a full-page image being applied, since the
+		 * FSM data is not in the page anyway.
+		 */
 		XLogRecordPageWithFreeSpace(rnode, blkno, freespace);
+	}
 }
 
 /*
@@ -8201,9 +8204,34 @@ heap_xlog_visible(XLogReaderState *record)
 		 * wal_log_hints enabled.)
 		 */
 	}
+
 	if (BufferIsValid(buffer))
+	{
+		Size		space = PageGetFreeSpace(BufferGetPage(buffer));
+
 		UnlockReleaseBuffer(buffer);
 
+		/*
+		 * Since FSM is not WAL-logged and only updated heuristically, it
+		 * easily becomes stale in standbys.  If the standby is later promoted
+		 * and runs VACUUM, it will skip updating individual free space
+		 * figures for pages that became all-visible (or all-frozen, depending
+		 * on the vacuum mode,) which is troublesome when FreeSpaceMapVacuum
+		 * propagates too optimistic free space values to upper FSM layers;
+		 * later inserters try to use such pages only to find out that they
+		 * are unusable.  This can cause long stalls when there are many such
+		 * pages.
+		 *
+		 * Forestall those problems by updating FSM's idea about a page that
+		 * is becoming all-visible or all-frozen.
+		 *
+		 * Do this regardless of a full-page image being applied, since the
+		 * FSM data is not in the page anyway.
+		 */
+		if (xlrec->flags & VISIBILITYMAP_VALID_BITS)
+			XLogRecordPageWithFreeSpace(rnode, blkno, space);
+	}
+
 	/*
 	 * Even if we skipped the heap page update due to the LSN interlock, it's
 	 * still safe to update the visibility map.  Any WAL record that clears