diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 06e91547dd..f17e80948d 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -576,10 +576,11 @@ XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking)
 		/*
 		 * Caller supplied a position to start at.
 		 *
-		 * In this case, NextRecPtr should already be pointing to a valid
-		 * record starting position.
+		 * In this case, NextRecPtr should already be pointing either to a
+		 * valid record starting position or alternatively to the beginning of
+		 * a page. See the header comments for XLogBeginRead.
 		 */
-		Assert(XRecOffIsValid(RecPtr));
+		Assert(RecPtr % XLOG_BLCKSZ == 0 || XRecOffIsValid(RecPtr));
 		randAccess = true;
 	}