diff --git a/web/flow-typed/npm/grpc-web_v1.x.x.js b/web/flow-typed/npm/grpc-web_v1.x.x.js
index e032b970a..965274c76 100644
--- a/web/flow-typed/npm/grpc-web_v1.x.x.js
+++ b/web/flow-typed/npm/grpc-web_v1.x.x.js
@@ -1,60 +1,97 @@
 // flow-typed signature: 7bfbf382213ab8a2a77e02cc8ce971e4
 // flow-typed version: <<STUB>>/grpc-web_v1.4.2/flow_v0.182.0
 
 declare module 'grpc-web' {
 
-  declare export type Metadata = { +[s: string]: string };
+  declare export type Metadata = { [s: string]: string };
 
   declare export type StatusCode =
     | 0   // OK
     | 1   // CANCELLED
     | 2   // UNKNOWN
     | 3   // INVALID_ARGUMENT
     | 4   // DEADLINE_EXCEEDED
     | 5   // NOT_FOUND
     | 6   // ALREADY_EXISTS
     | 7   // PERMISSION_DENIED
     | 8   // RESOURCE_EXHAUSTED
     | 9   // FAILED_PRECONDITION
     | 10  // ABORTED
     | 11  // OUT_OF_RANGE
     | 12  // UNIMPLEMENTED
     | 13  // INTERNAL
     | 14  // UNAVAILABLE
     | 15  // DATA_LOSS
     | 16; // UNAUTHENTICATED
 
   declare export type Status = {
     +code: number,
     +details: string,
     +metadata?: Metadata,
   };
 
+  declare export class UnaryInterceptor<REQ, RESP> {
+    intercept(
+      request: Request<REQ, RESP>,
+      invoker: (request: Request<REQ, RESP>) => Promise<UnaryResponse<REQ, RESP>>
+    ): Promise<UnaryResponse<REQ, RESP>>;
+  }
+
+  declare export class Request<REQ, RESP> {
+    getRequestMessage(): REQ;
+    getMethodDescriptor(): MethodDescriptor<REQ, RESP>;
+    getMetadata(): Metadata;
+    getCallOptions(): CallOptions;
+  }
+
+  declare export class UnaryResponse<REQ, RESP> {
+    getResponseMessage(): RESP;
+    getMetadata(): Metadata;
+    getMethodDescriptor(): MethodDescriptor<REQ, RESP>;
+    getStatus(): Status;
+  }
+
+  declare export class CallOptions {
+    constructor(options: { [index: string]: mixed; }): void;
+  }
+
+  declare export class MethodDescriptor<REQ, RESP> {
+    constructor(
+      name: string,
+      methodType: string,
+      requestType: (...args: mixed[]) => REQ,
+      responseType: (...args: mixed[]) => RESP,
+      requestSerializeFn: any,
+      responseDeserializeFn: any,
+    ): void;
+    getName(): string;
+  }
+
   declare export class RpcError extends Error {
     constructor(code: StatusCode, message: string, metadata: Metadata): void;
     code: StatusCode;
     metadata: Metadata;
   }
 
   declare export class ClientReadableStream<RESP> {
     on(eventType: "error", callback: (err: RpcError) => void): this;
     on(eventType: "status", callback: (status: Status) => void): this;
     on(eventType: "metadata", callback: (status: Metadata) => void): this;
     on(eventType: "data", callback: (response: RESP) => void): this;
     on(eventType: "end", callback: () => void): this;
 
     removeListener(eventType: "error", callback: (err: RpcError) => void): void;
     removeListener(
       eventType: "status",
       callback: (status: Status) => void,
     ): void;
     removeListener(
       eventType: "metadata",
       callback: (status: Metadata) => void,
     ): void;
     removeListener(eventType: "data", callback: (response: RESP) => void): void;
     removeListener(eventType: "end", callback: () => void): void;
     cancel(): void;
   }
 
 }