diff --git a/.travis.yml b/.travis.yml
index 91cc8141..3c627c85 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -59,8 +59,8 @@ script:
     - "echo 'backend : Agg' > $HOME/.matplotlib/matplotlibrc"
     - "echo 'backend.qt4 : PyQt4' >> $HOME/.matplotlib/matplotlibrc"
     # Run all tests
-    - python -c "import skimage, sys; sys.exit(skimage.test_verbose())"
-    - python -c "import skimage, sys; sys.exit(skimage.doctest_verbose())"
+    - python -c "import skimage, sys, io; sys.exit(skimage.test_verbose())"
+    - python -c "import skimage, sys, io; sys.exit(skimage.doctest_verbose())"
     # Run all doc examples
     - export PYTHONPATH=$(pwd):$PYTHONPATH
     - for f in doc/examples/*.py; do $PYTHON "$f"; if [ $? -ne 0 ]; then exit 1; fi done
diff --git a/Makefile b/Makefile
index e8a85587..2ace534e 100644
--- a/Makefile
+++ b/Makefile
@@ -7,10 +7,10 @@ clean:
 	find . -name "*.so" -o -name "*.pyc" -o -name "*.pyx.md5" | xargs rm -f
 
 test:
-	python -c "import skimage, sys; sys.exit(skimage.test_verbose())"
+	python -c "import skimage, sys, io; sys.exit(skimage.test_verbose())"
 
 doctest:
-	python -c "import skimage, sys; sys.exit(skimage.doctest_verbose())"
+	python -c "import skimage, sys, io; sys.exit(skimage.doctest_verbose())"
 
 coverage:
 	nosetests skimage --with-coverage --cover-package=skimage
diff --git a/skimage/__init__.py b/skimage/__init__.py
index 49510c91..f5697c84 100644
--- a/skimage/__init__.py
+++ b/skimage/__init__.py
@@ -89,6 +89,7 @@ else:
         if doctest:
             args.extend(['--with-doctest', '--ignore-files=^\.',
                         '--ignore-files=^setup\.py$$', '--ignore-files=test'])
+            # Make sure warnings do not break the doc tests
             with _warnings.catch_warnings():
                 _warnings.simplefilter("ignore")
                 success = nose.run('skimage', argv=args)