diff --git a/services/horizon/CHANGELOG.md b/services/horizon/CHANGELOG.md
index 2d3ebe7cb5..9724e52dc0 100644
--- a/services/horizon/CHANGELOG.md
+++ b/services/horizon/CHANGELOG.md
@@ -8,6 +8,7 @@ file. This project adheres to [Semantic Versioning](http://semver.org/).
 ### Code Changes
 
 * Fix bug in `horizon db reingest range` command, which would throw a duplicate entry conflict error from the DB. ([3661](https://github.com/stellar/go/pull/3661)).
+* Fix bug in DB metrics preventing Horizon from starting when read-only replica middleware is enabled. ([3668](https://github.com/stellar/go/pull/3668)).
 
 ## v2.4.0
 
diff --git a/services/horizon/internal/init.go b/services/horizon/internal/init.go
index c9c636faf3..97ab048f99 100644
--- a/services/horizon/internal/init.go
+++ b/services/horizon/internal/init.go
@@ -62,7 +62,7 @@ func mustInitHorizonDB(app *App) {
 		)}
 
 		app.primaryHistoryQ = &history.Q{mustNewDBSession(
-			db.HistorySubservice,
+			db.HistoryPrimarySubservice,
 			app.config.DatabaseURL,
 			maxIdle,
 			maxOpen,
diff --git a/support/db/metrics.go b/support/db/metrics.go
index 1733d2d1d7..5b322e80c8 100644
--- a/support/db/metrics.go
+++ b/support/db/metrics.go
@@ -19,6 +19,7 @@ var QueryTypeContextKey = CtxKey("query_type")
 type Subservice string
 
 var CoreSubservice = Subservice("core")
+var HistoryPrimarySubservice = Subservice("history_primary")
 var HistorySubservice = Subservice("history")
 var IngestSubservice = Subservice("ingest")