diff --git a/MANIFEST.in b/MANIFEST.in
index f314e9ae2..6b533819d 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -5,6 +5,7 @@ include *requirements.txt mypy.ini tox.ini
 include gittaggers.py Makefile cwltool.py
 recursive-include mypy-stubs *.pyi *.py
 include tests/*
+include tests/cwl-conformance/cwltool-conftest.py
 include tests/loop/*
 include tests/tmp1/tmp2/tmp3/.gitkeep
 include tests/tmp4/alpha/*