diff --git a/tests/btrfs/004 b/tests/btrfs/004
index 211d8bc2..670e1c23 100755
--- a/tests/btrfs/004
+++ b/tests/btrfs/004
@@ -58,7 +58,7 @@ _require_command "/usr/sbin/filefrag"
 rm -f $seqres.full
 
 FILEFRAG_FILTER='
-	if (/blocks of (\d+) bytes/) {
+	if (/blocks? of (\d+) bytes/) {
 		$blocksize = $1;
 		next
 	}