diff --git a/skimage/viewer/plugins/base.py b/skimage/viewer/plugins/base.py
index 14fda815..22ec3533 100644
--- a/skimage/viewer/plugins/base.py
+++ b/skimage/viewer/plugins/base.py
@@ -78,17 +78,14 @@ class Plugin(QtGui.QDialog):
         else:
             return param
 
-    def add_argument(self, name, low, high, **kwargs):
-        name, slider = self.add_slider(name, low, high, **kwargs)
-        self.arguments.append(slider)
-
-    def add_keyword_argument(self, name, low, high, **kwargs):
-        name, slider = self.add_slider(name, low, high, **kwargs)
-        self.keyword_arguments[name] = slider
-
-    def add_slider(self, name, low, high, **kwargs):
+    def add_widget(self, name, low, high, **kwargs):
         slider = Slider(name, low, high, **kwargs)
-        slider.callback = self.filter_image
+        if slider.ptype == 'kwarg':
+            self.keyword_arguments[name] = slider
+            slider.callback = self.filter_image
+        elif slider.ptype == 'arg':
+            self.keyword_arguments[name] = slider
+            self.arguments.append(slider)
         self.layout.addWidget(slider, self.row, 0)
         self.row += 1
         return name.replace(' ', '_'), slider
diff --git a/skimage/viewer/plugins/canny.py b/skimage/viewer/plugins/canny.py
index 08099795..278a7931 100644
--- a/skimage/viewer/plugins/canny.py
+++ b/skimage/viewer/plugins/canny.py
@@ -12,9 +12,9 @@ class CannyPlugin(OverlayPlugin):
         width = kwargs.get('width', 400)
         super(CannyPlugin, self).__init__(image_viewer,
                                           width=width, height=height)
-        self.add_keyword_argument('sigma', 0, 5, update_on='release')
-        self.add_keyword_argument('low_threshold', 0, 255, update_on='release')
-        self.add_keyword_argument('high_threshold', 0, 255, update_on='release')
+        self.add_widget('sigma', 0, 5, update_on='release')
+        self.add_widget('low_threshold', 0, 255, update_on='release')
+        self.add_widget('high_threshold', 0, 255, update_on='release')
         # Update image overlay to default slider values.
         self.filter_image()