diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 8222d77d..c0c21bd0 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -171,13 +171,15 @@ jobs:
 
       - name: Check if the `pythonbuild` crate changed
         id: check-pythonbuild
+        env:
+          BASE_REF: ${{ github.event.pull_request.base.ref || 'main' }}
         run: |
-          if git diff --quiet ${{ github.event.pull_request.base.sha || 'origin/main' }}...HEAD -- ':src/*.rs'; then
+          merge_base=$(git merge-base HEAD "origin/${BASE_REF}")
+          if git diff --quiet "${merge_base}...HEAD" -- ':src/*.rs'; then
               echo "changed=false" >> "$GITHUB_OUTPUT"
           else
               echo "changed=true" >> "$GITHUB_OUTPUT"
           fi
-          
 
   build-0:
     needs:
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 2b5841e7..af9a80f0 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -81,12 +81,16 @@ jobs:
 
       - name: Check if the `pythonbuild` crate changed
         id: check-pythonbuild
+        env:
+          BASE_REF: ${{ github.event.pull_request.base.ref || 'main' }}
         run: |
-          if git diff --quiet ${{ github.event.pull_request.base.sha || 'origin/main' }}...HEAD -- ':src/*.rs'; then
+          merge_base=$(git merge-base HEAD "origin/${BASE_REF}")
+          if git diff --quiet "${merge_base}...HEAD" -- ':src/*.rs'; then
               echo "changed=false" >> "$GITHUB_OUTPUT"
           else
               echo "changed=true" >> "$GITHUB_OUTPUT"
           fi
+
   build:
     needs:
       - generate-matrix
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 11434bb2..a7535c68 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -79,12 +79,13 @@ jobs:
             echo "any_builds=false" >> $GITHUB_OUTPUT
           fi
 
-
       - name: Check if the `pythonbuild` crate changed
         id: check-pythonbuild
-        shell: bash
+        env:
+          BASE_REF: ${{ github.event.pull_request.base.ref || 'main' }}
         run: |
-          if git diff --quiet ${{ github.event.pull_request.base.sha || 'origin/main' }}...HEAD -- ':src/*.rs'; then
+          merge_base=$(git merge-base HEAD "origin/${BASE_REF}")
+          if git diff --quiet "${merge_base}...HEAD" -- ':src/*.rs'; then
               echo "changed=false" >> "$GITHUB_OUTPUT"
           else
               echo "changed=true" >> "$GITHUB_OUTPUT"