diff --git a/src/matrix/calls/callEventTypes.ts b/src/matrix/calls/callEventTypes.ts
index ca5c870c..8fd7b23d 100644
--- a/src/matrix/calls/callEventTypes.ts
+++ b/src/matrix/calls/callEventTypes.ts
@@ -25,7 +25,7 @@ export const SDPStreamMetadataKey = "org.matrix.msc3077.sdp_stream_metadata";
 export interface CallDeviceMembership {
     device_id: string,
     session_id: string,
-    ["m.expires_ts"]?: number,
+    ["expires_ts"]?: number,
     feeds?: Array<{purpose: string}>
 }
 
diff --git a/src/matrix/calls/group/GroupCall.ts b/src/matrix/calls/group/GroupCall.ts
index f2561f32..0931d4ea 100644
--- a/src/matrix/calls/group/GroupCall.ts
+++ b/src/matrix/calls/group/GroupCall.ts
@@ -544,7 +544,7 @@ export class GroupCall extends EventEmitter<{change: never}> {
             callInfo["m.devices"].push({
                 ["device_id"]: this.options.ownDeviceId,
                 ["session_id"]: this.options.sessionId,
-                ["m.expires_ts"]: now + CALL_MEMBER_VALIDITY_PERIOD_MS,
+                ["expires_ts"]: now + CALL_MEMBER_VALIDITY_PERIOD_MS,
                 feeds: [{purpose: "m.usermedia"}]
             });
         }
diff --git a/src/matrix/calls/group/Member.ts b/src/matrix/calls/group/Member.ts
index 0aba3b54..9debef22 100644
--- a/src/matrix/calls/group/Member.ts
+++ b/src/matrix/calls/group/Member.ts
@@ -408,7 +408,7 @@ export class Member {
 }
 
 export function memberExpiresAt(callDeviceMembership: CallDeviceMembership): number | undefined {
-    const expiresAt = callDeviceMembership["m.expires_ts"];
+    const expiresAt = callDeviceMembership["expires_ts"];
     if (Number.isSafeInteger(expiresAt)) {
         return expiresAt;
     }