diff --git a/format.md b/format.md
index f0bd880..21f6312 100644
--- a/format.md
+++ b/format.md
@@ -73,8 +73,14 @@ Instruments contain a sample and some default parameters for that sample. Everyt
 ```
 Sample Length [Short]
 Volume [Byte]
+Flags [Byte]
 ADSR [Short]
 Sample
 ```
 
+The flags byte has the format:
+```
+            0 | 0000000
+| Sample Loop | unused
+```