diff --git a/.github/workflows/ccpp.yml b/.github/workflows/ccpp.yml
index 65124b16..fde688d7 100644
--- a/.github/workflows/ccpp.yml
+++ b/.github/workflows/ccpp.yml
@@ -12,13 +12,16 @@ jobs:
     steps:
     - uses: actions/checkout@v1
     - name: make check C99
-      run: make clean check CC="cc -std=c99 -Wno-unknown-warning-option -Werror"
+      run: make clean check -j 2 CC="cc -std=c99 -Wno-unknown-warning-option -Werror"
     - name: make check C11
       working-directory: ./tests
-      run: make clean check CC="cc -std=c11 -Wno-unknown-warning-option -Werror"
+      run: make clean check -j 2 CC="cc -std=c11 -Wno-unknown-warning-option -Werror"
     - name: make check C++
       working-directory: ./tests
-      run: make clean check CC="c++ -std=c++11"
+      run: make clean check -j 2 CC="c++ -std=c++11"
+    - name: make check against C++ STL
+      working-directory: ./tests
+      run: make clean check-stl -j 2
 
   build_linux32:
     runs-on: ubuntu-latest