diff --git a/README.md b/README.md
index 76ecc1271..917570d97 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,12 @@ Xcode to build or debug your projects you'll need to run this after you change
 gyp/gypi files.
 
     xb gyp
+    
+#### xethunk
+
+Updates the checked-in `src/cpu/xethunk/xethunk.bc` and `xethunk.ll` files.
+This is only required if changes are made to the xethunk files. The results
+should be checked in.
 
 #### build