diff --git a/client/sync.go b/client/sync.go
index 233313d4..b3f71310 100644
--- a/client/sync.go
+++ b/client/sync.go
@@ -232,6 +232,31 @@ func SyncStateHas(roomID string, check func(gjson.Result) bool) SyncCheckOpt {
 	}
 }
 
+// Check that the `state_after` section for `roomID` has an event which passes the check function.
+//
+// Note that the `state_after` section of a sync response will not contain the entire
+// state of the room for incremental or `lazy_load_members` syncs.
+func SyncStateAfterHas(roomID string, check func(gjson.Result) bool) SyncCheckOpt {
+	return func(clientUserID string, topLevelSyncJSON gjson.Result) error {
+		// Check the stable field
+		errStable := checkArrayElements(
+			topLevelSyncJSON, "rooms.join."+GjsonEscape(roomID)+".state_after.events", check,
+		)
+		// Check the unstable field
+		//
+		// FIXME: Some implementations haven't stabilized yet (Synapse) so we'll keep this
+		// here until then.
+		errUnstable := checkArrayElements(
+			topLevelSyncJSON, "rooms.join."+GjsonEscape(roomID)+"."+GjsonEscape("org.matrix.msc4222.state_after")+".events", check,
+		)
+		// Valid to find it in either place
+		if errStable == nil || errUnstable == nil {
+			return nil
+		}
+		return fmt.Errorf("SyncStateAfterHas(%s): Tried to check in the stable field: %s - and unstable field: %s", roomID, errStable, errUnstable)
+	}
+}
+
 func SyncEphemeralHas(roomID string, check func(gjson.Result) bool) SyncCheckOpt {
 	return func(clientUserID string, topLevelSyncJSON gjson.Result) error {
 		err := checkArrayElements(
diff --git a/tests/msc4140/delayed_event_test.go b/tests/msc4140/delayed_event_test.go
index 03557d88..6c93ffb5 100644
--- a/tests/msc4140/delayed_event_test.go
+++ b/tests/msc4140/delayed_event_test.go
@@ -30,16 +30,6 @@ const (
 	DelayedEventActionSend    = "send"
 )
 
-// A filter for `/sync` that excludes timeline events.
-//
-// This is useful if you want to see `state` in the `/sync` response without the pesky
-// de-duplication with `timeline` that traditional `/sync` does.
-const NoTimelineSyncFilter = `{
-		"room": {
-			"timeline": { "limit": 0 }
-	}
-}`
-
 // TODO: Test pagination of `GET /_matrix/client/v1/delayed_events` once
 // it is implemented in a homeserver.
 
@@ -195,7 +185,7 @@ func TestDelayedEvents(t *testing.T) {
 
 		// Check for the state change from the delayed state event (using `MustSyncUntil` to
 		// account for any processing or worker replication delays)
-		user.MustSyncUntil(t, client.SyncReq{Filter: NoTimelineSyncFilter}, client.SyncStateHas(roomID, func(ev gjson.Result) bool {
+		user.MustSyncUntil(t, client.SyncReq{UseStateAfter: true}, client.SyncStateAfterHas(roomID, func(ev gjson.Result) bool {
 			return ev.Get("type").Str == eventType && ev.Get("state_key").Str == stateKey
 		}))
 		// Make sure the state looks as expected after
@@ -347,7 +337,7 @@ func TestDelayedEvents(t *testing.T) {
 
 		// Check for the state change from the delayed state event (using `MustSyncUntil` to
 		// account for any processing or worker replication delays)
-		user.MustSyncUntil(t, client.SyncReq{Filter: NoTimelineSyncFilter}, client.SyncStateHas(roomID, func(ev gjson.Result) bool {
+		user.MustSyncUntil(t, client.SyncReq{UseStateAfter: true}, client.SyncStateAfterHas(roomID, func(ev gjson.Result) bool {
 			return ev.Get("type").Str == eventType && ev.Get("state_key").Str == stateKey
 		}))
 		// Make sure the state looks as expected after
@@ -417,7 +407,7 @@ func TestDelayedEvents(t *testing.T) {
 
 		// Check for the state change from the delayed state event (using `MustSyncUntil` to
 		// account for any processing or worker replication delays)
-		user.MustSyncUntil(t, client.SyncReq{Filter: NoTimelineSyncFilter}, client.SyncStateHas(roomID, func(ev gjson.Result) bool {
+		user.MustSyncUntil(t, client.SyncReq{UseStateAfter: true}, client.SyncStateAfterHas(roomID, func(ev gjson.Result) bool {
 			return ev.Get("type").Str == eventType && ev.Get("state_key").Str == stateKey
 		}))
 		// Make sure the state looks as expected after
@@ -512,7 +502,7 @@ func TestDelayedEvents(t *testing.T) {
 		// Sanity check that the room state was updated correctly with the delayed events
 		// that were sent. (using `MustSyncUntil` to account for any processing or worker
 		// replication delays)
-		user.MustSyncUntil(t, client.SyncReq{Filter: NoTimelineSyncFilter}, client.SyncStateHas(roomID, func(ev gjson.Result) bool {
+		user.MustSyncUntil(t, client.SyncReq{UseStateAfter: true}, client.SyncStateAfterHas(roomID, func(ev gjson.Result) bool {
 			return ev.Get("type").Str == eventType && ev.Get("state_key").Str == stateKey1
 		}))
 
@@ -528,7 +518,7 @@ func TestDelayedEvents(t *testing.T) {
 		// FIXME: Ideally, we'd check specifically for the last one that was sent but it
 		// will be a bit of a juggle and fiddly to get this right so for now we just check
 		// one.
-		user.MustSyncUntil(t, client.SyncReq{Filter: NoTimelineSyncFilter}, client.SyncStateHas(roomID, func(ev gjson.Result) bool {
+		user.MustSyncUntil(t, client.SyncReq{UseStateAfter: true}, client.SyncStateAfterHas(roomID, func(ev gjson.Result) bool {
 			return ev.Get("type").Str == eventType && ev.Get("state_key").Str == stateKey2
 		}))
 	})