diff --git a/devtools/server/actors/targets/browsing-context.js b/devtools/server/actors/targets/browsing-context.js
index c1a51667a32f..efa9a943c771 100644
--- a/devtools/server/actors/targets/browsing-context.js
+++ b/devtools/server/actors/targets/browsing-context.js
@@ -1346,25 +1346,6 @@ const browsingContextTargetPrototype = {
       isTopLevel: isTopLevel,
       id: getWindowID(window),
     });
-
-    // TODO bug 997119: move that code to ThreadActor by listening to
-    // window-ready
-    const threadActor = this.threadActor;
-    if (isTopLevel && threadActor.state != "detached") {
-      this.sources.reset();
-      threadActor.clearDebuggees();
-      threadActor.dbg.enable();
-      threadActor.maybePauseOnExceptions();
-      // Update the global no matter if the debugger is on or off,
-      // otherwise the global will be wrong when enabled later.
-      threadActor.global = window;
-    }
-
-    // Refresh the debuggee list when a new window object appears (top window or
-    // iframe).
-    if (threadActor.attached) {
-      threadActor.dbg.addDebuggees();
-    }
   },
 
   _windowDestroyed(window, id = null, isFrozen = false) {
@@ -1417,16 +1398,6 @@ const browsingContextTargetPrototype = {
       return;
     }
 
-    // Proceed normally only if the debuggee is not paused.
-    // TODO bug 997119: move that code to ThreadActor by listening to
-    // will-navigate
-    const threadActor = this.threadActor;
-    if (threadActor.state == "paused") {
-      threadActor.unsafeSynchronize(Promise.resolve(threadActor.doResume()));
-      threadActor.dbg.disable();
-    }
-    threadActor.disableAllBreakpoints();
-
     this.emit("tabNavigated", {
       url: newURI,
       nativeConsoleAPI: true,
@@ -1461,12 +1432,6 @@ const browsingContextTargetPrototype = {
       return;
     }
 
-    // TODO bug 997119: move that code to ThreadActor by listening to navigate
-    const threadActor = this.threadActor;
-    if (threadActor.state == "running") {
-      threadActor.dbg.enable();
-    }
-
     this.emit("tabNavigated", {
       url: this.url,
       title: this.title,
diff --git a/devtools/server/actors/thread.js b/devtools/server/actors/thread.js
index be756167301c..3074b6f9b746 100644
--- a/devtools/server/actors/thread.js
+++ b/devtools/server/actors/thread.js
@@ -138,6 +138,13 @@ const ThreadActor = ActorClassWithSpec(threadSpec, {
     this._onOpeningRequest = this._onOpeningRequest.bind(this);
     this._onNewDebuggee = this._onNewDebuggee.bind(this);
     this._eventBreakpointListener = this._eventBreakpointListener.bind(this);
+    this._onWindowReady = this._onWindowReady.bind(this);
+    this._onWillNavigate = this._onWillNavigate.bind(this);
+    this._onNavigate = this._onNavigate.bind(this);
+
+    this._parent.on("window-ready", this._onWindowReady);
+    this._parent.on("will-navigate", this._onWillNavigate);
+    this._parent.on("navigate", this._onNavigate);
 
     this._debuggerNotificationObserver = new DebuggerNotificationObserver();
 
@@ -282,6 +289,10 @@ const ThreadActor = ActorClassWithSpec(threadSpec, {
       } catch (e) {}
     }
 
+    this._parent.off("window-ready", this._onWindowReady);
+    this._parent.off("will-navigate", this._onWillNavigate);
+    this._parent.off("navigate", this._onNavigate);
+
     this.sources.off("newSource", this.onNewSourceEvent);
     this.clearDebuggees();
     this.conn.removeActorPool(this._threadLifetimePool);
@@ -1752,6 +1763,43 @@ const ThreadActor = ActorClassWithSpec(threadSpec, {
     return {};
   },
 
+  _onWindowReady: function({ isTopLevel, window }) {
+    if (isTopLevel && this.state != "detached") {
+      this.sources.reset();
+      this.clearDebuggees();
+      this.dbg.enabled = true;
+      this.maybePauseOnExceptions();
+      // Update the global no matter if the debugger is on or off,
+      // otherwise the global will be wrong when enabled later.
+      this.global = window;
+    }
+
+    // Refresh the debuggee list when a new window object appears (top window or
+    // iframe).
+    if (this.attached) {
+      this.dbg.addDebuggees();
+    }
+  },
+
+  _onWillNavigate: function({ isTopLevel }) {
+    if (!isTopLevel) {
+      return;
+    }
+
+    // Proceed normally only if the debuggee is not paused.
+    if (this.state == "paused") {
+      this.unsafeSynchronize(Promise.resolve(this.doResume()));
+      this.dbg.enabled = false;
+    }
+    this.disableAllBreakpoints();
+  },
+
+  _onNavigate: function() {
+    if (this.state == "running") {
+      this.dbg.enabled = true;
+    }
+  },
+
   // JS Debugger API hooks.
 
   /**
diff --git a/devtools/server/startup/worker.js b/devtools/server/startup/worker.js
index f8a62f56c29a..87cdffc87166 100644
--- a/devtools/server/startup/worker.js
+++ b/devtools/server/startup/worker.js
@@ -37,6 +37,7 @@ this.rpc = function(method, ...params) {
 loadSubScript("resource://devtools/shared/worker/loader.js");
 
 var defer = worker.require("devtools/shared/defer");
+var EventEmitter = worker.require("devtools/shared/event-emitter");
 var { ActorPool } = worker.require("devtools/server/actors/common");
 var { ThreadActor } = worker.require("devtools/server/actors/thread");
 var { WebConsoleActor } = worker.require("devtools/server/actors/webconsole");
@@ -97,6 +98,8 @@ this.addEventListener("message", function(event) {
         },
       };
 
+      EventEmitter.decorate(parent);
+
       const threadActor = new ThreadActor(parent, global);
       pool.addActor(threadActor);
 
diff --git a/devtools/server/tests/unit/testactors.js b/devtools/server/tests/unit/testactors.js
index b94a5d328a56..55202e190de1 100644
--- a/devtools/server/tests/unit/testactors.js
+++ b/devtools/server/tests/unit/testactors.js
@@ -16,6 +16,8 @@ const {
 const { TabSources } = require("devtools/server/actors/utils/TabSources");
 const makeDebugger = require("devtools/server/actors/utils/make-debugger");
 
+const noop = () => {};
+
 var gTestGlobals = new Set();
 DebuggerServer.addTestGlobal = function(global) {
   gTestGlobals.add(global);
@@ -122,6 +124,8 @@ function TestTargetActor(connection, global) {
 TestTargetActor.prototype = {
   constructor: TestTargetActor,
   actorPrefix: "TestTargetActor",
+  on: noop,
+  off: noop,
 
   get window() {
     return this._global;