diff --git a/HACKING.rst b/HACKING.rst
index 8e0ac44..76efd28 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -15,6 +15,8 @@
 - [T106] vim configuration should not be kept in source files.
 - [T107] Check that a service tag isn't in the module path
 - [T108] Check no hyphen at the end of rand_name() argument
+- [T109] Cannot use testtools.skip decorator; instead use
+         decorators.skip_because from tempest-lib
 - [N322] Method's default argument shouldn't be mutable
 
 Test Data/Configuration