diff --git a/doc/reference/scale.rst b/doc/reference/scale.rst
index 59e5fc8..161e5ea 100644
--- a/doc/reference/scale.rst
+++ b/doc/reference/scale.rst
@@ -1,6 +1,8 @@
 Scales
 ------
 
+.. automodule:: qwt.scale_map
+
 .. automodule:: qwt.scale_widget
 
 .. automodule:: qwt.scale_div