diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 21a89b6bc0e6206be6bcf30968d2363681485543..f38a1ac988ebb9016949c52dec91a08d50c6ca1a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -61,7 +61,7 @@ unittest_py3.8:
   image: python:3.8
   script: &python_test_script
     - touch ~/.pycaosdb.ini
-    - pip install nose pytest pytest-cov pytest-dateutil jsonschema==4.0.1
+    - pip install nose pytest pytest-cov python-dateutil jsonschema==4.0.1
     - pip install .
     - python -m pytest unittests