diff --git a/spec/integ/matrix-client-event-timeline.spec.ts b/spec/integ/matrix-client-event-timeline.spec.ts
index dbcb48acda7..ae542149338 100644
--- a/spec/integ/matrix-client-event-timeline.spec.ts
+++ b/spec/integ/matrix-client-event-timeline.spec.ts
@@ -29,9 +29,10 @@ import {
     Room,
 } from "../../src/matrix";
 import { logger } from "../../src/logger";
-import { encodeParams, encodeUri, QueryDict, replaceParam } from "../../src/utils";
+import { encodeParams, encodeUri, prefixUnstableParameters, QueryDict } from "../../src/utils";
 import { TestClient } from "../TestClient";
 import { FeatureSupport, Thread, THREAD_RELATION_TYPE, ThreadEvent } from "../../src/models/thread";
+import { Feature, ServerSupport } from "../../src/feature";
 import { emitPromise } from "../test-utils/test-utils";
 
 const userId = "@alice:localhost";
@@ -49,13 +50,11 @@ const withoutRoomId = (e: Partial<IEvent>): Partial<IEvent> => {
 /**
  * Our httpBackend only allows matching calls if we have the exact same query, in the exact same order
  * This method allows building queries with the exact same parameter order as the fetchRelations method in client
+ * @param supports features supported by our client
  * @param params query parameters
  */
-const buildRelationPaginationQuery = (params: QueryDict): string => {
-    if (Thread.hasServerSideFwdPaginationSupport === FeatureSupport.Experimental) {
-        params = replaceParam("dir", "org.matrix.msc3715.dir", params);
-    }
-    return "?" + encodeParams(params).toString();
+const buildRelationPaginationQuery = (supports: Map<Feature, ServerSupport>, params: QueryDict): string => {
+    return "?" + encodeParams(prefixUnstableParameters(supports, params)).toString();
 };
 
 const USER_MEMBERSHIP_EVENT = utils.mkMembership({
@@ -619,7 +618,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Backward, limit: 1 }),
+                        buildRelationPaginationQuery(client.canSupport, { dir: Direction.Backward, limit: 1 }),
                 )
                 .respond(200, function () {
                     return {
@@ -1789,7 +1788,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Backward, limit: 1 }),
+                        buildRelationPaginationQuery(client.canSupport, { dir: Direction.Backward, limit: 1 }),
                 )
                 .respond(200, function () {
                     return {
@@ -1847,7 +1846,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Backward, from: "start_token" }),
+                        buildRelationPaginationQuery(client.canSupport, { dir: Direction.Backward, from: "start_token" }),
                 )
                 .respond(200, function () {
                     return {
@@ -1861,7 +1860,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Forward, from: "end_token" }),
+                        buildRelationPaginationQuery(client.canSupport, { dir: Direction.Forward, from: "end_token" }),
                 )
                 .respond(200, function () {
                     return {
diff --git a/src/client.ts b/src/client.ts
index be9ede84559..0be03b81979 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -38,7 +38,7 @@ import { Filter, IFilterDefinition, IRoomEventFilter } from "./filter";
 import { CallEventHandlerEvent, CallEventHandler, CallEventHandlerEventHandlerMap } from "./webrtc/callEventHandler";
 import { GroupCallEventHandlerEvent, GroupCallEventHandlerEventHandlerMap } from "./webrtc/groupCallEventHandler";
 import * as utils from "./utils";
-import { replaceParam, QueryDict, sleep, noUnsafeEventProps, safeSet } from "./utils";
+import { QueryDict, sleep, noUnsafeEventProps, safeSet } from "./utils";
 import { Direction, EventTimeline } from "./models/event-timeline";
 import { IActionsObject, PushProcessor } from "./pushprocessor";
 import { AutoDiscovery, AutoDiscoveryAction } from "./autodiscovery";
@@ -7956,13 +7956,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         eventType?: EventType | string | null,
         opts: IRelationsRequestOpts = { dir: Direction.Backward },
     ): Promise<IRelationsResponse> {
-        let params = opts as QueryDict;
-        if (Thread.hasServerSideFwdPaginationSupport === FeatureSupport.Experimental) {
-            params = replaceParam("dir", "org.matrix.msc3715.dir", params);
-        }
-        if (this.canSupport.get(Feature.RelationsRecursion) === ServerSupport.Unstable) {
-            params = replaceParam("recurse", "org.matrix.msc3981.recurse", params);
-        }
+        const params = utils.prefixUnstableParameters(this.canSupport, opts as QueryDict);
         const queryString = utils.encodeParams(params);
 
         let templatedUrl = "/rooms/$roomId/relations/$eventId";
diff --git a/src/utils.ts b/src/utils.ts
index 326f87c38bc..1a0d6b7d137 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -25,6 +25,8 @@ import { Optional } from "matrix-events-sdk";
 import { IEvent, MatrixEvent } from "./models/event";
 import { M_TIMESTAMP } from "./@types/location";
 import { ReceiptType } from "./@types/read_receipts";
+import { Feature, ServerSupport } from "./feature";
+import { FeatureSupport, Thread } from "./models/thread";
 
 const interns = new Map<string, string>();
 
@@ -87,6 +89,16 @@ export function replaceParam(stable: string, unstable: string, dict: QueryDict):
     return result;
 }
 
+export function prefixUnstableParameters(supports: Map<Feature, ServerSupport>, params: QueryDict): QueryDict {
+    if (Thread.hasServerSideFwdPaginationSupport === FeatureSupport.Experimental) {
+        params = replaceParam("dir", "org.matrix.msc3715.dir", params);
+    }
+    if (supports.get(Feature.RelationsRecursion) === ServerSupport.Unstable) {
+        params = replaceParam("recurse", "org.matrix.msc3981.recurse", params);
+    }
+    return params;
+}
+
 /**
  * Decode a query string in `application/x-www-form-urlencoded` format.
  * @param query - A query string to decode e.g.