diff --git a/packages/react-server-dom-relay/src/ReactServerStreamConfigFB.js b/packages/react-server-dom-relay/src/ReactServerStreamConfigFB.js
index e0477fd6197e7..b13e5f3792601 100644
--- a/packages/react-server-dom-relay/src/ReactServerStreamConfigFB.js
+++ b/packages/react-server-dom-relay/src/ReactServerStreamConfigFB.js
@@ -17,6 +17,8 @@ export type Destination = {
 export type PrecomputedChunk = string;
 export type Chunk = string;
 
+export const isPrimaryStreamConfig = true;
+
 export function scheduleWork(callback: () => void) {
   // We don't schedule work in this model, and instead expect performWork to always be called repeatedly.
 }