diff --git a/.github/workflows/linux-ci.yml b/.github/workflows/linux-ci.yml
index 80572f818..b158776e0 100644
--- a/.github/workflows/linux-ci.yml
+++ b/.github/workflows/linux-ci.yml
@@ -8,14 +8,13 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
 
     steps:
     - uses: actions/checkout@v2
     - name: install dependencies
       run: sudo apt-get install pkg-config gcc ragel gcovr gtk-doc-tools libfreetype6-dev libglib2.0-dev libcairo2-dev libicu-dev libgraphite2-dev python3 python3-setuptools ninja-build gobject-introspection libgirepository1.0-dev
-    - run: sudo pip3 install fonttools
-    - run: sudo pip3 install git+https://github.com/mesonbuild/meson
+    - run: sudo pip3 install fonttools meson==0.47.0
     - name: run
       run: meson build -Db_coverage=true --auto-features=enabled -Dgraphite=enabled -Doptimization=2
     - name: ci
diff --git a/.github/workflows/msvc-ci.yml b/.github/workflows/msvc-ci.yml
index 4fae289a0..2dd722eda 100644
--- a/.github/workflows/msvc-ci.yml
+++ b/.github/workflows/msvc-ci.yml
@@ -2,7 +2,9 @@ name: msvc
 
 on:
   push:
+    branches: [ master ]
   pull_request:
+    branches: [ master ]
 
 jobs:
   msvc:
diff --git a/.github/workflows/msys2-ci.yml b/.github/workflows/msys2-ci.yml
index 26219b046..a0405e3f8 100644
--- a/.github/workflows/msys2-ci.yml
+++ b/.github/workflows/msys2-ci.yml
@@ -2,7 +2,9 @@ name: msys2
 
 on:
   push:
+    branches: [ master ]
   pull_request:
+    branches: [ master ]
 
 jobs:
   msys2:
diff --git a/test/fuzzing/meson.build b/test/fuzzing/meson.build
index 9eaf3fa99..9ddb4b2c7 100644
--- a/test/fuzzing/meson.build
+++ b/test/fuzzing/meson.build
@@ -36,7 +36,7 @@ test('shape_fuzzer', find_program('run-shape-fuzzer-tests.py'),
   args: [
     hb_shape_fuzzer_exe,
   ],
-  timeout: 60,
+  timeout: 300,
   depends: [hb_shape_fuzzer_exe, libharfbuzz, libharfbuzz_subset],
   workdir: join_paths(meson.current_build_dir(), '..', '..'),
   env: env,