diff --git a/.github/workflows/pytest-linux.yml b/.github/workflows/pytest-linux.yml
index ffa8872..2753693 100644
--- a/.github/workflows/pytest-linux.yml
+++ b/.github/workflows/pytest-linux.yml
@@ -11,9 +11,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-18.04, ubuntu-20.04]
+        os: [ubuntu-20.04, ubuntu-latest]
         python-version: [3.8, 3.x]
-        compiler_v: [7,8,9]
 
     steps:
     - uses: actions/checkout@v2
@@ -23,21 +22,11 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        sudo add-apt-repository ppa:ubuntu-toolchain-r/test  
-        sudo apt-get update
-        sudo apt-get install -y gcc-${{ matrix.compiler_v }} \
-                                g++-${{ matrix.compiler_v }}
         python -m pip install --upgrade pip
         python -m pip install pytest numpy
-        if [ "${{ matrix.compiler_v }}" == '7' ];then
-          pip install -e .[compression]
-        else
-          pip install -e .
-        fi
+        pip install -e .[compression]
       env:
         PYTHONPATH: $PWD
-        CC: gcc-${{ matrix.compiler_v }}
-        CXX: g++-${{ matrix.compiler_v }}
     - name: Run examples
       run: |
         python examples/use_classic.py
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 12129fd..0000000
--- a/requirements.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-.
-cython<=3.0.0
-versioneer
-flake8
diff --git a/setup.cfg b/setup.cfg
index 6192196..94c4304 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -7,5 +7,5 @@ tag_prefix = v
 
 [flake8]
 max-line-length = 90
-ignore = F403,E226,E731,W503,F405,E722,E741,W504,W605
+ignore = F403,E226,E731,E275,W503,F405,E722,E741,W504,W605
 exclude = versioneer.py,.git,.eggs
\ No newline at end of file
diff --git a/setup.py b/setup.py
index dd55ffb..1f569b8 100644
--- a/setup.py
+++ b/setup.py
@@ -35,7 +35,7 @@ def extensions():
 with open("README.md", "r") as fh:
     long_description = fh.read()
 
-s_required = ["cython>=0.17", "versioneer"]
+s_required = ["cython>=0.17,<=3.0.0", "versioneer", "flake8"]
 i_required = ["contexttimer"]
 
 configuration = {