diff --git a/.github/workflows/appimage.yml b/.github/workflows/appimage.yml
index 14e30c8d..091e4c1c 100644
--- a/.github/workflows/appimage.yml
+++ b/.github/workflows/appimage.yml
@@ -67,4 +67,6 @@ jobs:
     - name: Regression Tests
       run: |
         export RATARMOUNT_CMD=/usr/local/bin/ratarmount
-        bash tests/runtests.sh
+        PARALLELIZATION=1 bash tests/runtests.sh &
+        PARALLELIZATION=2 bash tests/runtests.sh &
+        PARALLELIZATION=0 bash tests/runtests.sh &
diff --git a/tests/runtests.sh b/tests/runtests.sh
index c346157a..e78bc687 100755
--- a/tests/runtests.sh
+++ b/tests/runtests.sh
@@ -13,6 +13,9 @@ RATARMOUNT_CMD="$RATARMOUNT_CMD --index-minimum-file-count 0"
 export RATARMOUNT_CMD
 echo "RATARMOUNT_CMD: $RATARMOUNT_CMD"
 
+if [[ -z "$PARALLELIZATIONS" ]]; then
+    PARALLELIZATIONS="1 2 0"
+fi
 
 # MAC does not have mountpoint check!
 if ! command -v mountpoint &>/dev/null; then
@@ -1890,7 +1893,7 @@ pytestedTests+=(
 )
 
 
-for parallelization in 1 2 0; do
+for parallelization in $PARALLELIZATIONS; do
 
 echo "== Testing with -P $parallelization =="
 export parallelization