diff --git a/docs/api.rst b/docs/api.rst
index d5af1f03..a16e85a5 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -152,3 +152,8 @@ pipelines
 ^^^^^^^^^^^
 .. automodule:: mmocr.datasets.pipelines
     :members:
+
+utils
+^^^^^^^^^^^
+.. automodule:: mmocr.datasets.utils
+    :members:
diff --git a/requirements/readthedocs.txt b/requirements/readthedocs.txt
index fad43ef7..6c528f87 100644
--- a/requirements/readthedocs.txt
+++ b/requirements/readthedocs.txt
@@ -1,5 +1,6 @@
 imgaug
 kwarray
+lanms-proper
 lmdb
 matplotlib
 mmcv