diff --git a/config/c-code/tox.ini.j2 b/config/c-code/tox.ini.j2
index 66d36e8..692d7d2 100644
--- a/config/c-code/tox.ini.j2
+++ b/config/c-code/tox.ini.j2
@@ -29,6 +29,7 @@ envlist =
 {% include 'tox-testenv.j2' %}
 
 [testenv:coverage]
+usedevelop = true
 basepython = %(coverage_basepython)s
 allowlist_externals =
     mkdir