diff --git a/src/backend/access/brin/brin.c b/src/backend/access/brin/brin.c
index 442a46140db..b0e89ace5e2 100644
--- a/src/backend/access/brin/brin.c
+++ b/src/backend/access/brin/brin.c
@@ -190,7 +190,8 @@ brininsert(Relation idxRel, Datum *values, bool *nulls,
 				AutoVacuumRequestWork(AVW_BRINSummarizeRange,
 									  RelationGetRelid(idxRel),
 									  lastPageRange);
-			brin_free_tuple(lastPageTuple);
+			else
+				LockBuffer(buf, BUFFER_LOCK_UNLOCK);
 		}
 
 		brtup = brinGetTupleForHeapBlock(revmap, heapBlk, &buf, &off,
diff --git a/src/backend/access/brin/brin_revmap.c b/src/backend/access/brin/brin_revmap.c
index fc8b10ab396..e778cbcacdc 100644
--- a/src/backend/access/brin/brin_revmap.c
+++ b/src/backend/access/brin/brin_revmap.c
@@ -179,13 +179,16 @@ brinSetHeapBlockItemptr(Buffer buf, BlockNumber pagesPerRange,
 /*
  * Fetch the BrinTuple for a given heap block.
  *
- * The buffer containing the tuple is locked, and returned in *buf. As an
- * optimization, the caller can pass a pinned buffer *buf on entry, which will
- * avoid a pin-unpin cycle when the next tuple is on the same page as a
- * previous one.
+ * The buffer containing the tuple is locked, and returned in *buf.  The
+ * returned tuple points to the shared buffer and must not be freed; if caller
+ * wants to use it after releasing the buffer lock, it must create its own
+ * palloc'ed copy.  As an optimization, the caller can pass a pinned buffer
+ * *buf on entry, which will avoid a pin-unpin cycle when the next tuple is on
+ * the same page as a previous one.
  *
  * If no tuple is found for the given heap range, returns NULL. In that case,
- * *buf might still be updated, but it's not locked.
+ * *buf might still be updated (and pin must be released by caller), but it's
+ * not locked.
  *
  * The output tuple offset within the buffer is returned in *off, and its size
  * is returned in *size.