diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index b0b79f4..09e95e1 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -8,6 +8,8 @@ jobs:
     name: "coverage"
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: recursive
     - name: Install lcov by Homebrew
       run: brew install lcov
     - name: Build && Test && Upload
diff --git a/.github/workflows/darwin.yml b/.github/workflows/darwin.yml
index 85a0aeb..07e86ea 100644
--- a/.github/workflows/darwin.yml
+++ b/.github/workflows/darwin.yml
@@ -16,6 +16,8 @@ jobs:
     name: "xcode-${{matrix.config.xcode}}"
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: recursive
     - name: Select Xcode
       run: sudo xcode-select --switch "/Applications/Xcode_${{matrix.config.xcode}}.app"
     - name: Build && Test
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 8d7085b..c785bc7 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -24,6 +24,8 @@ jobs:
       run: sudo apt-get -y install "${{matrix.config.cc}}" "${{matrix.config.cxx}}"
     - name: Checkout
       uses: actions/checkout@v2
+      with:
+        submodules: recursive
     - name: Build && Test
       run: .ci/build_linux.sh
       env: { CC: "${{matrix.config.cc}}", CXX: "${{matrix.config.cxx}}" }
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 1c48908..1486034 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -17,5 +17,7 @@ jobs:
     name: "${{matrix.config.vs}} ${{matrix.config.arch}}"
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: recursive
     - name: Build && Test
       run: .ci\build_windows_${{matrix.config.arch}}.bat