diff --git a/sys/vfs/ntfs/ntfs_compr.c b/sys/vfs/ntfs/ntfs_compr.c
--- a/sys/vfs/ntfs/ntfs_compr.c
+++ b/sys/vfs/ntfs/ntfs_compr.c
@@ -89,6 +89,8 @@
 			ctag >>= 1;
 		}
 	}
+	if (pos < NTFS_COMPBLOCK_SIZE)
+		bzero(buf + pos, NTFS_COMPBLOCK_SIZE - pos);
 	return len + 3;
 }