diff --git a/.github/workflows/CI_cmake.yml b/.github/workflows/CI_cmake.yml
index 0ac33d9..7c5e162 100644
--- a/.github/workflows/CI_cmake.yml
+++ b/.github/workflows/CI_cmake.yml
@@ -21,6 +21,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
+    - name: Install Eigen
+      run: sudo apt install libeigen3-dev
 
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.