diff --git a/skimage/__init__.py b/skimage/__init__.py
index f5f97130..14b3e448 100644
--- a/skimage/__init__.py
+++ b/skimage/__init__.py
@@ -158,7 +158,9 @@ else:
 
 
 if sys.version.startswith('2.6'):
-    warnings.warn("Python 2.6 is deprecated and will not be supported in scikit-image 0.13+", stacklevel=2)
+    msg = ("Python 2.6 is deprecated and will not be supported in"
+           "scikit-image 0.13+")
+    warnings.warn(msg, stacklevel=2)
 
 
 del warnings, functools, osp, imp, sys
diff --git a/skimage/_shared/_warnings.py b/skimage/_shared/_warnings.py
index 522a0e89..d397d8e9 100644
--- a/skimage/_shared/_warnings.py
+++ b/skimage/_shared/_warnings.py
@@ -7,11 +7,13 @@ import re
 __all__ = ['all_warnings', 'expected_warnings', 'warn']
 
 
-def warn(message, **kwargs):
+def warn(message, category=None, stacklevel=2):
     """A version of `warnings.warn` with a default stacklevel of 2.
     """
-    kwargs.setdefault('stacklevel', 2)
-    warnings.warn(message, **kwargs)
+    if category is not None:
+        warnings.warn(message, category=category, stacklevel=stacklevel)
+    else:
+        warnings.warn(message, stacklevel=stacklevel)
 
 
 @contextmanager
diff --git a/skimage/measure/_ccomp.pyx b/skimage/measure/_ccomp.pyx
index 0da764fb..e7088d24 100644
--- a/skimage/measure/_ccomp.pyx
+++ b/skimage/measure/_ccomp.pyx
@@ -4,7 +4,7 @@
 #cython: wraparound=False
 
 import numpy as np
-import warnings
+from .._shared.utils import warn
 
 cimport numpy as cnp
 
@@ -47,9 +47,9 @@ ctypedef struct bginfo:
 
 cdef void get_bginfo(background_val, bginfo *ret) except *:
     if background_val is None:
-        warnings.warn(DeprecationWarning(
+        warn(DeprecationWarning(
                 'The default value for `background` will change to 0 in v0.12'
-            ), stacklevel=2)
+            ))
         ret.background_val = -1
     else:
         ret.background_val = background_val
diff --git a/skimage/viewer/utils/core.py b/skimage/viewer/utils/core.py
index 8bffaafe..c44f0991 100644
--- a/skimage/viewer/utils/core.py
+++ b/skimage/viewer/utils/core.py
@@ -8,7 +8,7 @@ from matplotlib.colors import LinearSegmentedColormap
 
 if has_qt and 'agg' not in mpl.get_backend().lower():
     warn("Recommended matplotlib backend is `Agg` for full "
-                  "skimage.viewer functionality.")
+         "skimage.viewer functionality.")
 
 
 __all__ = ['init_qtapp', 'start_qtapp', 'RequiredAttr', 'figimage',