diff --git a/packages/element-web-playwright-common/src/testcontainers/synapse.ts b/packages/element-web-playwright-common/src/testcontainers/synapse.ts
index 55ef890f7d..efcae3ef88 100644
--- a/packages/element-web-playwright-common/src/testcontainers/synapse.ts
+++ b/packages/element-web-playwright-common/src/testcontainers/synapse.ts
@@ -176,9 +176,11 @@ const DEFAULT_CONFIG = {
          */
         msc4143_enabled: false,
     },
-    matrix_rtc: {
-        transports: Array<{ type: string; [field: string]: string }>,
-    },
+    matrix_rtc: undefined as
+        | undefined
+        | {
+              transports: Array<{ type: string; [field: string]: string }>;
+          },
     oidc_providers: [],
     serve_server_wellknown: true,
     presence: {