Fix rebar3 debug logging
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f41059e..cfd4c49 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,10 +18,8 @@
         os: [ubuntu-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     env:
-      # Set to 1 for verbose rebar3 logging
-      DEBUG: 0
-      # Set to 1 for even more verbose rebar3 logging
-      DIAGNOSTIC: 0
+      # Define to something other than empty string to enable verbose rebar3 logging
+      DEBUG: ''
     steps:
       - name: Check out repository code
         uses: actions/checkout@v2