diff --git a/.github/workflows/astronomy-engine-tests.yml b/.github/workflows/astronomy-engine-tests.yml
index 2e65138c..9d7d7964 100644
--- a/.github/workflows/astronomy-engine-tests.yml
+++ b/.github/workflows/astronomy-engine-tests.yml
@@ -20,7 +20,7 @@ jobs:
       with:
         python-version: '3.10'
     - name: Install Python tools
-      run: python -m pip install --upgrade pip && pip install mypy
+      run: python -m pip install --upgrade pip && pip install mypy mpmath
     - name: Install documentation tools Linux
       if: startsWith(matrix.os, 'ubuntu')
       run: sudo apt install -y doxygen xsltproc cppcheck