diff --git a/pgxn/neon/pagestore_smgr.c b/pgxn/neon/pagestore_smgr.c
index 317871bb78..f4468786fe 100644
--- a/pgxn/neon/pagestore_smgr.c
+++ b/pgxn/neon/pagestore_smgr.c
@@ -3064,6 +3064,14 @@ neon_end_unlogged_build(SMgrRelation reln)
 		/* Make the relation look permanent again */
 		reln->smgr_relpersistence = RELPERSISTENCE_PERMANENT;
 
+		/*
+		 * Drop all buffers of the relation from buffer cache. They have valid contents, so it's a bit sad to throw
+		 * them away, but they might be marked as !BM_PERMANENT, which is no longer true and could cause
+		 * trouble afterwards. Also, there's a race condition with checkpoint and the mdunlink call below: The
+		 * checkpointer uses mdexists() to check if the buffer belongs to an unlogged relation, and then writes
+		 * the page to disk if it exists, but we might unlink the file in between the mdexists() and mdwrite() calls,
+		 * causing the write to fail.
+		  */
 		{
 			static ForkNumber forks[] = { MAIN_FORKNUM, FSM_FORKNUM, VISIBILITYMAP_FORKNUM };
 			static BlockNumber blocks[] = { 0, 0, 0 };