diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8e265dc0..8d5f4b55 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -16,6 +16,7 @@ env:
   OPENSSL_INSTALL_PATH: ${{ github.workspace }}/bin/ssl
   OPENSSL_SOURCE_PATH: ${{ github.workspace }}/src/openssl
   PYTHON_INSTALL_PATH: ${{ github.workspace }}/bin/python
+  PYTHON_SOURCE_PATH: ${{ github.workspace }}/src/cpython
 
 jobs:
   build: