diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 780052a..52240aa 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,6 +57,10 @@ jobs:
           python -m pip install --upgrade setuptools pip wheel
           python -m pip install .[test]
 
+      - name: Install iisignature for testing
+        run: |
+          python -m pip install iisignature
+
       - name: Test package
         run: >-
           python -m pytest -ra --cov --cov-report=xml --cov-report=term