diff --git a/.github/workflows/linux_build_tests.yaml b/.github/workflows/linux_build_tests.yaml
index ecdf38bfe4e8e4d6201c5aebe91bbb42429cdca1..3f5c575df3d86e2eeae494770c1938ce8f2f5104 100644
--- a/.github/workflows/linux_build_tests.yaml
+++ b/.github/workflows/linux_build_tests.yaml
@@ -3,13 +3,12 @@ name: linux builds
 on:
   push:
     branches:
-    - master
     - develop
     - releases/**
   pull_request:
     branches:
-    - master
     - develop
+    - releases/**
     paths-ignore:
       # Don't run if we only modified packages in the built-in repository
       - 'var/spack/repos/builtin/**'
diff --git a/.github/workflows/macos_unit_tests.yaml b/.github/workflows/macos_unit_tests.yaml
index 38feb2fc6ad119e297d428315f6df36bdaa9a3eb..f1e856070c537bccdc02e740dcd30c37aa6dcd17 100644
--- a/.github/workflows/macos_unit_tests.yaml
+++ b/.github/workflows/macos_unit_tests.yaml
@@ -3,13 +3,12 @@ name: macos tests
 on:
   push:
     branches:
-      - master
       - develop
       - releases/**
   pull_request:
     branches:
-      - master
       - develop
+      - releases/**
 jobs:
   build:
 
diff --git a/.github/workflows/minimum_python_versions.yaml b/.github/workflows/minimum_python_versions.yaml
index 474f0915148f3e64ddbc0420c21610851da6647d..a6ab5dfa4059bd0aa19dbf993ae55d26a93e0d0b 100644
--- a/.github/workflows/minimum_python_versions.yaml
+++ b/.github/workflows/minimum_python_versions.yaml
@@ -3,13 +3,12 @@ name: python version check
 on:
   push:
     branches:
-      - master
       - develop
       - releases/**
   pull_request:
     branches:
-      - master
       - develop
+      - releases/**
 jobs:
   validate:
 
diff --git a/.travis.yml b/.travis.yml
index df4262bf1e8c45d498137e2aebc636890f590127..e4e6383dbdc7896e355b8ab81c8e35cb97847e4a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,6 @@
-# Only build master and develop on push; do not build every branch.
+# Only build releases and develop on push; do not build every branch.
 branches:
   only:
-    - master
     - develop
     - /^releases\/.*$/
 
diff --git a/lib/spack/spack/ci.py b/lib/spack/spack/ci.py
index 55d311d6a500d23a71a0a7563013c346072a473a..732b985dd154a26fcc0941f15d49e5116b337bde 100644
--- a/lib/spack/spack/ci.py
+++ b/lib/spack/spack/ci.py
@@ -493,7 +493,7 @@ def generate_gitlab_ci_yaml(env, print_summary, output_file,
     after_script = None
     if custom_spack_repo:
         if not custom_spack_ref:
-            custom_spack_ref = 'master'
+            custom_spack_ref = 'develop'
         before_script = [
             ('git clone "{0}"'.format(custom_spack_repo)),
             'pushd ./spack && git checkout "{0}" && popd'.format(