diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
index 0e74be37..b243e07c 100644
--- a/.github/workflows/nix.yml
+++ b/.github/workflows/nix.yml
@@ -32,6 +32,7 @@ on:
 
 jobs:
   build:
+    if: (github.event_name != 'pull_request' && ! github.event.pull_request.head.repo.fork) || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork)
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
diff --git a/.github/workflows/stack-nix.yml b/.github/workflows/stack-nix.yml
index 0ded71c2..40dc18a3 100644
--- a/.github/workflows/stack-nix.yml
+++ b/.github/workflows/stack-nix.yml
@@ -36,6 +36,7 @@ on:
 
 jobs:
   linux:
+    if: (github.event_name != 'pull_request' && ! github.event.pull_request.head.repo.fork) || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork)
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
diff --git a/.github/workflows/stack.yml b/.github/workflows/stack.yml
index e629e2dd..a1b9c52a 100644
--- a/.github/workflows/stack.yml
+++ b/.github/workflows/stack.yml
@@ -34,6 +34,7 @@ on:
 
 jobs:
   linux:
+    if: (github.event_name != 'pull_request' && ! github.event.pull_request.head.repo.fork) || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork)
     runs-on: ubuntu-20.04
     strategy:
       fail-fast: false