diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 71675513a..52786c2fa 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -23,7 +23,7 @@ jobs:
     - name: Compile
       run: ./bootstrap
     - name: CT tests
-      run: ./rebar3 ct
+      run: DIAGNOSTIC=1 ./rebar3 ct
     - shell: bash
       name: Dialyzer
       run: |