diff --git a/.coveragerc b/.coveragerc
index 2515d6b9..c5619672 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,6 +1,7 @@
 [run]
 branch = True
+source = dulwich
 
 [report]
 exclude_lines =
     raise NotImplementedError
diff --git a/.travis.yml b/.travis.yml
index 8a798655..302eeec4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,41 +1,41 @@
 language: python
 sudo: false
 cache: pip
 
 python:
   - 2.7
   - 3.3
   - 3.4
   - 3.5
   - 3.5-dev
   - 3.6
   - 3.6-dev
   - pypy3.3-5.2-alpha1
   - pypy3.5
 
 env:
   - PYTHONHASHSEED=random
     TEST_REQUIRE="gevent greenlet geventhttpclient fastimport"
 
 matrix:
   include:
     - python: pypy
       env: TEST_REQUIRE=fastimport
 
 install:
   - travis_retry pip install -U pip coverage codecov flake8 $TEST_REQUIRE
 
 script:
   # Test without c extensions
-  - python -m coverage run -p --source=dulwich -m unittest dulwich.tests.test_suite
+  - python -m coverage run -p -m unittest dulwich.tests.test_suite
 
   # Test with c extensions
   - python setup.py build_ext -i
-  - python -m coverage run -p --source=dulwich -m unittest dulwich.tests.test_suite
+  - python -m coverage run -p -m unittest dulwich.tests.test_suite
 
   # Style
   - make style
 
 after_success:
   - python -m coverage combine
   - codecov
diff --git a/Makefile b/Makefile
index 706ab0ac..8054ee2c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,71 +1,71 @@
 PYTHON = python -Werror
 PYFLAKES = pyflakes
 PEP8 = pep8
 FLAKE8 ?= flake8
 SETUP = $(PYTHON) setup.py
 PYDOCTOR ?= pydoctor
 TESTRUNNER ?= unittest
 RUNTEST = PYTHONHASHSEED=random PYTHONPATH=$(shell pwd)$(if $(PYTHONPATH),:$(PYTHONPATH),) $(PYTHON) -m $(TESTRUNNER) $(TEST_OPTIONS)
 COVERAGE = python3-coverage
 
 DESTDIR=/
 
 all: build
 
 doc:: pydoctor
 doc:: sphinx
 
 sphinx::
 	$(MAKE) -C docs html
 
 pydoctor::
 	$(PYDOCTOR) --make-html -c dulwich.cfg
 
 build::
 	$(SETUP) build
 	$(SETUP) build_ext -i
 
 install::
 	$(SETUP) install --root="$(DESTDIR)"
 
 check:: build
 	$(RUNTEST) dulwich.tests.test_suite
 
 check-tutorial:: build
 	$(RUNTEST) dulwich.tests.tutorial_test_suite
 
 check-nocompat:: build
 	$(RUNTEST) dulwich.tests.nocompat_test_suite
 
 check-compat:: build
 	$(RUNTEST) dulwich.tests.compat_test_suite
 
 check-pypy:: clean
 	$(MAKE) check-noextensions PYTHON=pypy
 
 check-noextensions:: clean
 	$(RUNTEST) dulwich.tests.test_suite
 
 check-all: check check-pypy check-noextensions
 
 clean::
 	$(SETUP) clean --all
 	rm -f dulwich/*.so
 
 flakes:
 	$(PYFLAKES) dulwich
 
 pep8:
 	$(PEP8) dulwich
 
 style:
 	$(FLAKE8) --exclude=build,.git,build-pypy,.tox
 
 before-push: check
 	git diff origin/master | $(PEP8) --diff
 
 coverage:
-	$(COVERAGE) run --source=dulwich -m unittest dulwich.tests.test_suite dulwich.contrib.test_suite
+	$(COVERAGE) run -m unittest dulwich.tests.test_suite dulwich.contrib.test_suite
 
 coverage-html: coverage
 	$(COVERAGE) html