diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 22cd2440..1f97441c 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-13, macos-12]
+        os: [macos-12]
         python-version: ["3.11"]
     runs-on: ${{ matrix.os }}
     steps:
@@ -54,11 +54,14 @@ jobs:
       working-directory: tests
       run: |
         export PATH=$PATH:/Users/runner/work/gmtsar/gmtsar/GMTSAR/bin
-        # remove Google Colab specific commands
-        sed -i '' '/if \x27google\.colab\x27 in sys\.modules:/,/^$/d' imperial_valley_2015.py
-        sed -i '' 's/^[[:blank:]]*!.*$//' imperial_valley_2015.py
         ulimit -n 10000
-        python3 imperial_valley_2015.py
+        # remove Google Colab specific commands and add __main__ section
+        cat imperial_valley_2015.py \
+            | sed '/if \x27google\.colab\x27 in sys\.modules:/,/^$/d' \
+            | sed 's/^[[:blank:]]*!.*$//' \
+            | awk '/username = \x27GoogleColab2023\x27/ {print "if __name__ == \x27__main__\x27:"; indent=1} {if(indent) sub(/^/, "    "); print}' \
+            > imperial_valley_2015.fixed.py
+        python3 imperial_valley_2015.fixed.py
     - name: Archive test results
       uses: actions/upload-artifact@v3
       with:
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 87401d02..c6ad6520 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -71,10 +71,13 @@ jobs:
         Xvfb :99 -screen 0 800x600x24 > /dev/null 2>&1 &
         export DISPLAY=:99
         export XVFB_PID=$!
-        # remove Google Colab specific commands
-        sed -i '/if \x27google\.colab\x27 in sys\.modules:/,/^$/d' imperial_valley_2015.py
-        sed -i 's/^[[:blank:]]*!.*$//' imperial_valley_2015.py
-        python3 imperial_valley_2015.py
+        # remove Google Colab specific commands and add __main__ section
+        cat imperial_valley_2015.py \
+            | sed '/if \x27google\.colab\x27 in sys\.modules:/,/^$/d' \
+            | sed 's/^[[:blank:]]*!.*$//' \
+            | awk '/username = \x27GoogleColab2023\x27/ {print "if __name__ == \x27__main__\x27:"; indent=1} {if(indent) sub(/^/, "    "); print}' \
+            > imperial_valley_2015.fixed.py
+        python3 imperial_valley_2015.fixed.py
     - name: Archive test results
       uses: actions/upload-artifact@v3
       with: