diff --git a/lib/matplotlib/backend_tools.py b/lib/matplotlib/backend_tools.py
index 231820b29484..27119a5b80dc 100644
--- a/lib/matplotlib/backend_tools.py
+++ b/lib/matplotlib/backend_tools.py
@@ -77,9 +77,9 @@ class ToolBase(object):
     """
 
     def __init__(self, toolmanager, name):
-        _log.warning('Treat the new Tool classes introduced in v1.5 as '
-                     'experimental for now, the API will likely change in '
-                     'version 2.1, and some tools might change name')
+        cbook._warn_external(
+            'The new Tool classes introduced in v1.5 are experimental; their '
+            'API (including names) will likely change in future versions.')
         self._name = name
         self._toolmanager = toolmanager
         self._figure = None