diff --git a/doc/HACKING.md b/doc/HACKING.md
index 620fb5f24..68080fc9e 100644
--- a/doc/HACKING.md
+++ b/doc/HACKING.md
@@ -191,7 +191,7 @@ A modern desktop can build and run through all the tests in a couple of minutes
 
 Adjust `-j` and `PYTEST_PAR` accordingly for your hardware.
 
-There are three kinds of tests:
+There are four kinds of tests:
 
 * **source tests** - run by `make check-source`, looks for whitespace,
   header order, and checks formatted quotes from BOLTs if BOLTDIR