diff --git a/.github/workflows/cov.yml b/.github/workflows/cov.yml
index 438396f0..44261804 100644
--- a/.github/workflows/cov.yml
+++ b/.github/workflows/cov.yml
@@ -22,7 +22,7 @@ jobs:
   cov:
     runs-on: macos-11
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Fetch Boost superproject
       run: |
         cd ..
diff --git a/.github/workflows/fast.yml b/.github/workflows/fast.yml
index b4219dd6..236b0c99 100644
--- a/.github/workflows/fast.yml
+++ b/.github/workflows/fast.yml
@@ -32,7 +32,7 @@ jobs:
         os: [ubuntu-latest, windows-latest, macos-latest]
       fail-fast: true
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: prepare build
       run: |
         mkdir build
diff --git a/.github/workflows/slow.yml b/.github/workflows/slow.yml
index ecf4b041..0c2a8b4d 100644
--- a/.github/workflows/slow.yml
+++ b/.github/workflows/slow.yml
@@ -25,7 +25,7 @@ jobs:
   appleclang:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Fetch Boost superproject
       run: |
         cd ..
@@ -46,13 +46,13 @@ jobs:
         cd libs/histogram
         ../../b2 $B2_OPTS cxxstd=17 test//all
 
-  gcc5:
-    runs-on: ubuntu-18.04
+  gcc7:
+    runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: egor-tensin/setup-gcc@v1
       with:
-        version: 5
+        version: 7
     - name: Fetch Boost superproject
       run: |
         cd ..
@@ -60,6 +60,7 @@ jobs:
         cd boost
         mv -f $GITHUB_WORKSPACE/* libs/histogram
         git submodule update --init --depth 5 tools/build tools/boostdep
+        git submodule update --init --depth 5 libs/format
         python tools/boostdep/depinst/depinst.py --git_args "--depth 5 --jobs 3" histogram
         mv -f * $GITHUB_WORKSPACE
     - name: Prepare b2
@@ -67,12 +68,12 @@ jobs:
     - name: Test cxxstd=14 (warnings ignored)
       run: |
         cd libs/histogram
-        ../../b2 -q -j2 toolset=gcc-5 cxxstd=14 test//all examples
+        ../../b2 -q -j2 toolset=gcc-7 cxxstd=14 test//all examples
 
   gcc10:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Fetch Boost superproject
       run: |
         cd ..
@@ -80,6 +81,7 @@ jobs:
         cd boost
         mv -f $GITHUB_WORKSPACE/* libs/histogram
         git submodule update --init --depth 5 tools/build tools/boostdep
+        git submodule update --init --depth 5 libs/format
         python tools/boostdep/depinst/depinst.py --git_args "--depth 5 --jobs 3" histogram
         mv -f * $GITHUB_WORKSPACE
     - name: Prepare b2
@@ -92,7 +94,7 @@ jobs:
   clang14:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Fetch Boost superproject
       run: |
         cd ..
diff --git a/.github/workflows/superproject_cmake.yml b/.github/workflows/superproject_cmake.yml
index f97ffb16..a5f2de3c 100644
--- a/.github/workflows/superproject_cmake.yml
+++ b/.github/workflows/superproject_cmake.yml
@@ -14,7 +14,7 @@ jobs:
   build:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Fetch Boost superproject
       run: |
         cd ..
diff --git a/.gitignore b/.gitignore
index 408de80c..922f7f45 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,3 +13,4 @@ tools/codecov
 coverage-report
 .cache
 venv
+.pytest_cache
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 67fa7b26..b7ad7964 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,8 +2,8 @@
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
-# We support CMake 3.5, but prefer 3.16 policies and behavior
-cmake_minimum_required(VERSION 3.5...3.16)
+# We support CMake 3.12, but prefer 3.27 policies and behavior
+cmake_minimum_required(VERSION 3.12...3.27)
 
 project(boost_histogram VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 337da698..0d6a71f4 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -2,7 +2,7 @@
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
-find_package(PythonInterp)
+find_package(Python3)
 if (PYTHONINTERP_FOUND)
   # checks that b2 and cmake are in sync
   add_test(NAME runpy-${PROJECT_NAME}_check_build_system COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/check_build_system.py)
@@ -152,4 +152,4 @@ if (NOT(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERS
 
 endif()
 
-endif()
\ No newline at end of file
+endif()