diff --git a/sloth/plugins/__init__.py b/sloth/plugins/__init__.py
index 6c33bff..a62638d 100644
--- a/sloth/plugins/__init__.py
+++ b/sloth/plugins/__init__.py
@@ -85,3 +85,27 @@ class CopyAnnotationsPlugin(QObject):
 
     def action(self):
         return self._sc
+
+
+class PolygonEnumeratorPlugin(QObject):
+    """Enumerate the corners of polygons."""
+
+    def __init__(self, labeltool):
+        QObject.__init__(self)
+
+        # Decorate the paint() method with our enumerating paint:
+        from sloth.items import PolygonItem
+        oldpaint = PolygonItem.paint
+
+        def paint(self, painter, option, widget=None):
+            oldpaint(self, painter, option, widget)
+            for i, p in enumerate(self._polygon):
+                painter.drawText(p, str(i))
+
+        import functools
+        functools.update_wrapper(paint, oldpaint)
+
+        PolygonItem.paint = paint
+
+    def action(self):
+        return None