diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 161c2e2d3df..ebf237bf575 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -1175,6 +1175,10 @@ AllocSetFree(void *pointer)
 		link = GetFreeListLink(chunk);
 
 #ifdef MEMORY_CONTEXT_CHECKING
+		/* Test for previously-freed chunk */
+		if (unlikely(chunk->requested_size == InvalidAllocSize))
+			elog(WARNING, "detected double pfree in %s %p",
+				 set->header.name, chunk);
 		/* Test for someone scribbling on unused space in chunk */
 		if (chunk->requested_size < GetChunkSizeFromFreeListIdx(fidx))
 			if (!sentinel_ok(pointer, chunk->requested_size))