diff --git a/docs/operations/metrics.md b/docs/operations/metrics.md
index 83cc95506900..dc2ee952813c 100644
--- a/docs/operations/metrics.md
+++ b/docs/operations/metrics.md
@@ -119,6 +119,7 @@ Most metric values reset each emission period, as specified in `druid.monitoring
 |`query/failed/count`|Number of failed queries.|This metric is only available if the `QueryCountStatsMonitor` module is included.||
 |`query/interrupted/count`|Number of queries interrupted due to cancellation.|This metric is only available if the `QueryCountStatsMonitor` module is included.||
 |`query/timeout/count`|Number of timed out queries.|This metric is only available if the `QueryCountStatsMonitor` module is included.||
+|`mergeBuffer/pendingRequests`|Number of requests waiting to acquire a batch of buffers from the merge buffer pool.|This metric is only available if the `QueryCountStatsMonitor` module is included.||
 
 ### Jetty