diff --git a/scikits/image/morphology/watershed.py b/scikits/image/morphology/watershed.py
index 3b72d834..28441710 100644
--- a/scikits/image/morphology/watershed.py
+++ b/scikits/image/morphology/watershed.py
@@ -30,6 +30,7 @@ import scipy.ndimage
 from ..filter import rank_order
 
 import _watershed
+import warnings
 
 def fast_watershed(image, markers, connectivity=None, offset=None, mask=None):
     """
@@ -362,6 +363,9 @@ def __heapify_markers(markers, image):
 def _slow_watershed(image, markers, connectivity=8, mask=None):
     """Return a matrix labeled using the watershed algorithm
     
+    Use the `watershed` function for a faster execution.
+    This pure Python function is solely for pedagogical purposes.
+    
     Parameters
     ----------
     image: 2-d ndarray of integers