diff --git a/CHANGELOG.md b/CHANGELOG.md
index b8bf9761d64..d54703eb3f1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,9 @@
 
 * **Graphite**: Add Metrictank dashboard to Graphite datasource
 
+## Breaking changes
+* **PagerDuty**: Change `payload.custom_details` field in PagerDuty notification to be a JSON object instead of a string.
+
 # 6.5.2 (2019-12-11)
 
 ### Bug Fixes