diff --git a/remote/domains/ContentProcessDomain.jsm b/remote/domains/ContentProcessDomain.jsm
index 997691acaae3..9ef2622805bb 100644
--- a/remote/domains/ContentProcessDomain.jsm
+++ b/remote/domains/ContentProcessDomain.jsm
@@ -10,19 +10,9 @@ const { Domain } = ChromeUtils.import(
   "chrome://remote/content/domains/Domain.jsm"
 );
 
-ChromeUtils.defineModuleGetter(
-  this,
-  "ContextObserver",
-  "chrome://remote/content/observers/ContextObserver.jsm"
-);
-
 class ContentProcessDomain extends Domain {
   destructor() {
     super.destructor();
-
-    if (this._contextObserver) {
-      this._contextObserver.destructor();
-    }
   }
 
   // helpers
@@ -38,11 +28,4 @@ class ContentProcessDomain extends Domain {
   get chromeEventHandler() {
     return this.docShell.chromeEventHandler;
   }
-
-  get contextObserver() {
-    if (!this._contextObserver) {
-      this._contextObserver = new ContextObserver(this.chromeEventHandler);
-    }
-    return this._contextObserver;
-  }
 }
diff --git a/remote/domains/content/Page.jsm b/remote/domains/content/Page.jsm
index 5687e22db41e..87c6a4232dfa 100644
--- a/remote/domains/content/Page.jsm
+++ b/remote/domains/content/Page.jsm
@@ -43,12 +43,12 @@ class Page extends ContentProcessDomain {
     this._onFrameNavigated = this._onFrameNavigated.bind(this);
     this._onScriptLoaded = this._onScriptLoaded.bind(this);
 
-    this.contextObserver.on("script-loaded", this._onScriptLoaded);
+    this.session.contextObserver.on("script-loaded", this._onScriptLoaded);
   }
 
   destructor() {
     this.setLifecycleEventsEnabled({ enabled: false });
-    this.contextObserver.off("script-loaded", this._onScriptLoaded);
+    this.session.contextObserver.off("script-loaded", this._onScriptLoaded);
     this.disable();
 
     super.destructor();
@@ -59,7 +59,10 @@ class Page extends ContentProcessDomain {
   async enable() {
     if (!this.enabled) {
       this.enabled = true;
-      this.contextObserver.on("frame-navigated", this._onFrameNavigated);
+      this.session.contextObserver.on(
+        "frame-navigated",
+        this._onFrameNavigated
+      );
 
       this.chromeEventHandler.addEventListener("readystatechange", this, {
         mozSystemGroup: true,
@@ -87,7 +90,10 @@ class Page extends ContentProcessDomain {
 
   disable() {
     if (this.enabled) {
-      this.contextObserver.off("frame-navigated", this._onFrameNavigated);
+      this.session.contextObserver.off(
+        "frame-navigated",
+        this._onFrameNavigated
+      );
 
       this.chromeEventHandler.removeEventListener("readystatechange", this, {
         mozSystemGroup: true,
diff --git a/remote/domains/content/Runtime.jsm b/remote/domains/content/Runtime.jsm
index a2a95812d083..ede7c7ca02c0 100644
--- a/remote/domains/content/Runtime.jsm
+++ b/remote/domains/content/Runtime.jsm
@@ -62,14 +62,20 @@ class Runtime extends ContentProcessDomain {
     this._onContextCreated = this._onContextCreated.bind(this);
     this._onContextDestroyed = this._onContextDestroyed.bind(this);
     // TODO Bug 1602083
-    this.contextObserver.on("context-created", this._onContextCreated);
-    this.contextObserver.on("context-destroyed", this._onContextDestroyed);
+    this.session.contextObserver.on("context-created", this._onContextCreated);
+    this.session.contextObserver.on(
+      "context-destroyed",
+      this._onContextDestroyed
+    );
   }
 
   destructor() {
     this.disable();
-    this.contextObserver.off("context-created", this._onContextCreated);
-    this.contextObserver.off("context-destroyed", this._onContextDestroyed);
+    this.session.contextObserver.off("context-created", this._onContextCreated);
+    this.session.contextObserver.off(
+      "context-destroyed",
+      this._onContextDestroyed
+    );
     super.destructor();
   }
 
diff --git a/remote/sessions/ContentProcessSession.jsm b/remote/sessions/ContentProcessSession.jsm
index 39a9ca98d96d..1aaa822001bd 100644
--- a/remote/sessions/ContentProcessSession.jsm
+++ b/remote/sessions/ContentProcessSession.jsm
@@ -13,6 +13,12 @@ const { DomainCache } = ChromeUtils.import(
   "chrome://remote/content/domains/DomainCache.jsm"
 );
 
+ChromeUtils.defineModuleGetter(
+  this,
+  "ContextObserver",
+  "chrome://remote/content/observers/ContextObserver.jsm"
+);
+
 class ContentProcessSession {
   constructor(messageManager, browsingContext, content, docShell) {
     this.messageManager = messageManager;
@@ -29,11 +35,22 @@ class ContentProcessSession {
   }
 
   destructor() {
+    this._contextObserver?.destructor();
+
     this.messageManager.removeMessageListener("remote:request", this);
     this.messageManager.removeMessageListener("remote:destroy", this);
     this.domains.clear();
   }
 
+  get contextObserver() {
+    if (!this._contextObserver) {
+      this._contextObserver = new ContextObserver(
+        this.docShell.chromeEventHandler
+      );
+    }
+    return this._contextObserver;
+  }
+
   // Domain event listener
 
   onEvent(eventName, params) {