diff --git a/.github/workflows/vtest.yml b/.github/workflows/vtest.yml
index 4cdbdce5b..b75329dbd 100644
--- a/.github/workflows/vtest.yml
+++ b/.github/workflows/vtest.yml
@@ -75,6 +75,9 @@ jobs:
       run: make -C addons/wurfl/dummy
     - name: Compile HAProxy with ${{ matrix.CC }}
       run: |
+        echo "::group::Show platform specific defines"
+        echo | ${{ matrix.CC }} -dM -xc -E -
+        echo "::endgroup::"
         make -j$(nproc) all \
           ERR=1 \
           TARGET=${{ matrix.TARGET }} \
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 42bb4e8c9..4d14d4817 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -51,6 +51,9 @@ jobs:
           zlib-devel
     - name: Compile HAProxy with ${{ matrix.CC }}
       run: |
+        echo "::group::Show platform specific defines"
+        echo | ${{ matrix.CC }} -dM -xc -E -
+        echo "::endgroup::"
         make -j$(nproc) all \
           ERR=1 \
           TARGET=${{ matrix.TARGET }} \