diff --git a/doc/expansion.rst b/doc/expansion.rst
index 4dc38171e7ffd73aca485f24e958feab57ad3f5f..b2a7aebf5c9e752f9cbcf6fdebba8517e2bc8ac2 100644
--- a/doc/expansion.rst
+++ b/doc/expansion.rst
@@ -3,6 +3,11 @@ Expansions
 
 .. automodule:: sumpy.expansion
 
+Differential Operators
+----------------------
+
+.. automodule:: sumpy.expansion.diff_op
+
 Local Expansions
 ----------------