diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d4f7b0a..2f932bb 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -27,10 +27,10 @@ jobs:
         pip install -r requirements-dev.txt
 
     - name: Validate against psf/black
-      run: python -m black --check pdfplumber
+      run: python -m black --check pdfplumber tests
 
     - name: Validate against flake8
-      run: python -m flake8 pdfplumber
+      run: python -m flake8 pdfplumber tests
 
   test:
     needs: lint
diff --git a/Makefile b/Makefile
index f740e6b..1faaed0 100644
--- a/Makefile
+++ b/Makefile
@@ -14,12 +14,12 @@ tests:
 	${PYTHON} -m coverage html
 
 check-black:
-	${PYTHON} -m black pdfplumber --check
+	${PYTHON} -m black --check pdfplumber tests
 
 check-flake:
-	${PYTHON} -m flake8 pdfplumber
+	${PYTHON} -m flake8 pdfplumber tests
 
 lint: check-flake check-black
 
 format:
-	${PYTHON} -m black pdfplumber
+	${PYTHON} -m black pdfplumber tests