diff --git a/src/bin/pg_basebackup/streamutil.c b/src/bin/pg_basebackup/streamutil.c
index 99daf0e972..6602858491 100644
--- a/src/bin/pg_basebackup/streamutil.c
+++ b/src/bin/pg_basebackup/streamutil.c
@@ -309,7 +309,10 @@ RetrieveWalSegSize(PGconn *conn)
 		return false;
 	}
 
-	/* fetch xlog value and unit from the result */
+	/*
+	 * Fetch xlog value and unit from the result. Can't overflow since the unit
+	 * is at most two characters.
+	 */
 	if (sscanf(PQgetvalue(res, 0, 0), "%d%s", &xlog_val, xlog_unit) != 2)
 	{
 		pg_log_error("WAL segment size could not be parsed");