diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c643f3f4..f4d074752 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unrelease]
+
+### Added
+
+- `/drop_mempool_tx` endpoint to notify event observers when a mempool
+  transaction has been removed the mempool.
+- `"reward_slot_holders"` field to the `new_burn_block` event
+
 ## [2.0.6] - 2021-02-15
 
 The database schema has not changed since 2.0.5, so when spinning up a
diff --git a/docs/event-dispatcher.md b/docs/event-dispatcher.md
index 0ae939530..1826a7eff 100644
--- a/docs/event-dispatcher.md
+++ b/docs/event-dispatcher.md
@@ -128,3 +128,25 @@ Example:
   "0x80800000000400f942874ce525e87f21bbe8c121b12fac831d02f4000000000000000000000000000003e800006ae29867aec4b0e4f776bebdcea7f6d9a24eeff370c8c739defadfcbb52659b30736ad4af021e8fb741520a6c65da419fdec01989fdf0032fc1838f427a9a36102010000000000051ac2d519faccba2e435f3272ff042b89435fd160ff00000000000003e800000000000000000000000000000000000000000000000000000000000000000000"
 ]
 ```
+
+
+### `POST /drop_mempool_tx`
+
+This payload includes raw transactions newly received in the
+node's mempool.
+
+Example:
+
+```json
+{
+  "dropped_txids": ["d7b667bb93898b1d3eba4fee86617b06b95772b192f3643256dd0821b476e36f"],
+  "reason": "ReplaceByFee"
+}
+```
+
+Reason can be one of:
+
+* `ReplaceByFee` - replaced by a transaction with the same nonce, but a higher fee
+* `ReplaceAcrossFork` - replaced by a transaction with the same nonce but in the canonical fork
+* `TooExpensive` - the transaction is too expensive to include in a block
+* `StaleGarbageCollect` - transaction was dropped because it became stale