diff --git a/package-lock.json b/package-lock.json
index 4f9b683..a941bdb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -6,7 +6,7 @@
   "dependencies": {
     "@sinonjs/formatio": {
       "version": "2.0.0",
-      "resolved": "https://registry.npmjs.org/@sinonjs/formatio/-/formatio-2.0.0.tgz",
+      "resolved": "http://registry.npmjs.org/@sinonjs/formatio/-/formatio-2.0.0.tgz",
       "integrity": "sha512-ls6CAMA6/5gG+O/IdsBcblvnd8qcO/l1TYoNeAzp3wcISOxlPXQEus0mLcdwazEkWjaBdaJ3TaxmNgCLWwvWzg==",
       "dev": true,
       "requires": {
@@ -1679,7 +1679,7 @@
     },
     "event-stream": {
       "version": "3.3.4",
-      "resolved": "https://registry.npmjs.org/event-stream/-/event-stream-3.3.4.tgz",
+      "resolved": "http://registry.npmjs.org/event-stream/-/event-stream-3.3.4.tgz",
       "integrity": "sha1-SrTJoPWlTbkzi0w02Gv86PSzVXE=",
       "dev": true,
       "requires": {
@@ -5364,9 +5364,9 @@
       }
     },
     "rxjs": {
-      "version": "5.5.6",
-      "resolved": "https://registry.npmjs.org/rxjs/-/rxjs-5.5.6.tgz",
-      "integrity": "sha512-v4Q5HDC0FHAQ7zcBX7T2IL6O5ltl1a2GX4ENjPXg6SjDY69Cmx9v4113C99a4wGF16ClPv5Z8mghuYorVkg/kg==",
+      "version": "5.5.8",
+      "resolved": "https://registry.npmjs.org/rxjs/-/rxjs-5.5.8.tgz",
+      "integrity": "sha512-Bz7qou7VAIoGiglJZbzbXa4vpX5BmTTN2Dj/se6+SwADtw4SihqBIiEa7VmTXJ8pynvq0iFr5Gx9VLyye1rIxQ==",
       "requires": {
         "symbol-observable": "1.0.1"
       }
diff --git a/package.json b/package.json
index bf40196..b79b0fd 100644
--- a/package.json
+++ b/package.json
@@ -58,6 +58,6 @@
   },
   "dependencies": {
     "eventemitter3": "^2.0.3",
-    "rxjs": "^5.5.6"
+    "rxjs": "^5.5.8"
   }
 }
diff --git a/src/participant.ts b/src/participant.ts
index 95129a4..1a927d3 100644
--- a/src/participant.ts
+++ b/src/participant.ts
@@ -307,7 +307,7 @@ export class Participant extends EventEmitter {
    * the RPC system.
    */
   private attachListeners() {
-    this.rpc = new RPC(this.frame.contentWindow, '1.0');
+    this.rpc = new RPC(this.frame.contentWindow!, '1.0');
 
     this.rpc.expose('sendInteractivePacket', data => {
       this.websocket!.send(
diff --git a/src/reactive.ts b/src/reactive.ts
index 9a8f10f..7456999 100644
--- a/src/reactive.ts
+++ b/src/reactive.ts
@@ -42,7 +42,7 @@ export class MemorizingSubject<T> extends Subject<T> {
   }
 
   // tslint:disable-next-line
-  protected _subscribe(subscriber: Subscriber<T>): Subscription {
+  _subscribe(subscriber: Subscriber<T>): Subscription {
     const subscription = super._subscribe(subscriber);
     if (subscription && this.hasSet && !(<ISubscription>subscription).closed) {
       subscriber.next(this.value);