diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49b9372..027078c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -162,6 +162,7 @@ jobs:
           file: ${{ steps.coverage.outputs.file }}
           format: cobertura
           flag-name: Scala ${{ matrix.scala }}
+          parallel: true
 
       # Scanned once, on the first Scala version only: SonarQube tracks one analysis per branch, so
       # running it per matrix leg would have the legs overwrite each other.
@@ -191,6 +192,20 @@ jobs:
             -Dsonar.scala.coverage.reportPaths=${{ steps.sonar.outputs.reports }}
             ${{ inputs.sonar_args }}
 
+  # Closes the parallel Coveralls build once every matrix leg has uploaded its part. Without
+  # `parallel: true` the first upload closes the build and the other legs get rejected with
+  # "Can't add a job to a build that is already closed".
+  coverage-finished:
+    runs-on: ubuntu-latest
+    needs: [test-coverage]
+    if: ${{ !cancelled() }}
+
+    steps:
+      - name: finish Coveralls build
+        uses: coverallsapp/github-action@v2
+        with:
+          parallel-finished: true
+
   binary-compatibility:
     runs-on: ubuntu-latest
     strategy: