diff --git a/CHANGES.md b/CHANGES.md
index c885b691..127309b9 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,13 @@
 # Release notes #
 
+## [v0.9.1](https://github.com/open2c/cooler/compare/v0.9.0...v0.9.1)
+
+Date 2023-01-23
+
+### Maintenance
+
+* Export `_IndexingMixin` from `cooler.core` to keep private API used by cooltools.
+
 ## [v0.9.0](https://github.com/open2c/cooler/compare/v0.8.11...v0.9.0)
 
 Date 2023-01-18
diff --git a/cooler/_version.py b/cooler/_version.py
index c7afb700..a49ca91a 100644
--- a/cooler/_version.py
+++ b/cooler/_version.py
@@ -1,4 +1,4 @@
-__version__ = "0.9.0"
+__version__ = "0.9.1"
 __format_version__ = 3
 __format_version_mcool__ = 2
 __format_version_scool__ = 1