diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 2a88afd9183e9..3cd9f6650e705 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -113,7 +113,7 @@ jobs:
         name: mpy-cross.static-x64-windows
         path: mpy-cross/mpy-cross.static.exe
     - name: Upload mpy-cross builds to S3
-      if: github.event_name == 'push' || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
+      if: (github.event_name == 'push' && github.ref == 'refs/heads/main' && github.repository_owner == 'adafruit') || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
       env:
         AWS_PAGER: ''
         AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
@@ -190,7 +190,7 @@ jobs:
         AWS_PAGER: ''
         AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
         AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-      if: github.event_name == 'push' || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
+      if: (github.event_name == 'push' && github.ref == 'refs/heads/main' && github.repository_owner == 'adafruit') || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
 
 
   build-arm:
@@ -431,7 +431,7 @@ jobs:
         AWS_PAGER: ''
         AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
         AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-      if: github.event_name == 'push' || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
+      if: (github.event_name == 'push' && github.ref == 'refs/heads/main' && github.repository_owner == 'adafruit') || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
 
   build-riscv:
     runs-on: ubuntu-20.04
@@ -482,7 +482,7 @@ jobs:
         AWS_PAGER: ''
         AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
         AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-      if: github.event_name == 'push' || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
+      if: (github.event_name == 'push' && github.ref == 'refs/heads/main' && github.repository_owner == 'adafruit') || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
   build-xtensa:
     runs-on: ubuntu-20.04
     needs: test
@@ -590,4 +590,4 @@ jobs:
         AWS_PAGER: ''
         AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
         AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-      if: github.event_name == 'push' || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))
+      if: (github.event_name == 'push' && github.ref == 'refs/heads/main' && github.repository_owner == 'adafruit') || (github.event_name == 'release' && (github.event.action == 'published' || github.event.action == 'rerequested'))