diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index da184e05d..61fd760de 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -43,7 +43,13 @@ jobs:
         run: bundle config set --local version system
       - name: bundle install
         run: |
+          # TEMP DIAGNOSTIC: print the inherited MAKEFLAGS before clearing it.
+          echo "DEBUG MAKEFLAGS=[$env:MAKEFLAGS]"
+          echo "DEBUG MFLAGS=[$env:MFLAGS]"
+          $env:MAKEFLAGS = ''
           bundle config set without profilers libs
           bundle install
       - name: compile
-        run: bundle exec rake compile
+        run: |
+          $env:MAKEFLAGS = ''
+          bundle exec rake compile