diff --git a/.flake8 b/.flake8
new file mode 100644
index 000000000..4f6e9562b
--- /dev/null
+++ b/.flake8
@@ -0,0 +1,16 @@
+
+15 lines (14 sloc) 290 Bytes
+[flake8]
+ignore = E203, E266, E501, E731, W503
+max-line-length = 80
+select = B,C,E,F,W,T4,B9
+exclude =
+    .env,
+    .git,
+    __pycache__,
+    lemmatizer.py,
+    lookup.py,
+    _tokenizer_exceptions_list.py,
+    spacy/lang/fr/lemmatizer,
+    spacy/lang/nb/lemmatizer
+    spacy/__init__.py
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 9410d6a8b..9ffd60a87 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -54,13 +54,15 @@ jobs:
       versionSpec: '$(python.version)'
       architecture: 'x64'
 
+  # Downgrading pip is necessary to prevent a wheel version incompatiblity.
+  # Might be fixed in the future or some other way, so investigate again.
   - script: |
       python -m pip install --upgrade pip==18.1
       pip install -r requirements.txt
     displayName: 'Install dependencies'
 
-  # - script: python -m flake8 . --count --exclude=spacy/compat.py,spacy/lang --select=E901,E999,F821,F822,F823 --show-source --statistics
-  #   displayName: 'flake8'
+  - script: python -m flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
+    displayName: 'flake8'
 
   - script: |
       python setup.py build_ext --inplace
diff --git a/requirements.txt b/requirements.txt
index a505dded1..567872472 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,3 +12,4 @@ requests>=2.13.0,<3.0.0
 pytest>=4.0.0,<4.1.0
 mock>=2.0.0,<3.0.0
 pathlib==1.0.1; python_version < "3.4"
+flake8>=3.5.0,<3.6.0