--- a/toolkit/components/extensions/ExtensionChild.jsm
+++ b/toolkit/components/extensions/ExtensionChild.jsm
@@ -85,35 +85,43 @@ function injectAPI(source, dest) {
  * A finalization witness helper that wraps a sendMessage response and
  * guarantees to either get the promise resolved, or rejected when the
  * wrapped promise goes out of scope.
  *
  * Holding a reference to a returned StrongPromise doesn't prevent the
  * wrapped promise from being garbage collected.
  */
 const StrongPromise = {
+  locations: new Map(),
+
   wrap(promise, channelId, location) {
     return new Promise((resolve, reject) => {
-      const tag = `${channelId}|${location}`;
-      const witness = finalizationService.make("extensions-sendMessage-witness", tag);
+      this.locations.set(channelId, location);
+
+      const witness = finalizationService.make("extensions-sendMessage-witness", channelId);
       promise.then(value => {
+        this.locations.delete(channelId);
         witness.forget();
         resolve(value);
       }, error => {
+        this.locations.delete(channelId);
         witness.forget();
         reject(error);
       });
     });
   },
-  observe(subject, topic, tag) {
-    const pos = tag.indexOf("|");
-    const channel = Number(tag.substr(0, pos));
-    const location = tag.substr(pos + 1);
-    const message = `Promised response from onMessage listener at ${location} went out of scope`;
-    MessageChannel.abortChannel(channel, {message});
+  observe(subject, topic, channelId) {
+    channelId = Number(channelId);
+    let location = this.locations.get(channelId);
+    this.locations.delete(channelId);
+
+    const message = `Promised response from onMessage listener went out of scope`;
+    const error = ChromeUtils.createError(message, location);
+    error.mozWebExtLocation = location;
+    MessageChannel.abortChannel(channelId, error);
   },
 };
 Services.obs.addObserver(StrongPromise, "extensions-sendMessage-witness");
 
 /**
  * Abstraction for a Port object in the extension API.
  *
  * @param {BaseContext} context The context that owns this port.
@@ -391,17 +399,17 @@ class Messenger {
 
   sendNativeMessage(messageManager, msg, recipient, responseCallback) {
     msg = NativeApp.encodeMessage(this.context, msg);
     return this.sendMessage(messageManager, msg, recipient, responseCallback);
   }
 
   _onMessage(name, filter) {
     return new EventManager(this.context, name, fire => {
-      const [location] = new this.context.cloneScope.Error().stack.split("\n", 1);
+      const caller = this.context.getCaller();
 
       let listener = {
         messageFilterPermissive: this.optionalFilter,
         messageFilterStrict: this.filter,
 
         filterMessage: (sender, recipient) => {
           // Exclude messages coming from content scripts for the devtools extension contexts
           // (See Bug 1383310).
@@ -435,19 +443,19 @@ class Messenger {
           sendResponse = Cu.exportFunction(sendResponse, this.context.cloneScope);
 
           // Note: We intentionally do not use runSafe here so that any
           // errors are propagated to the message sender.
           let result = fire.raw(message, sender, sendResponse);
           message = null;
 
           if (result instanceof this.context.cloneScope.Promise) {
-            return StrongPromise.wrap(result, channelId, location);
+            return StrongPromise.wrap(result, channelId, caller);
           } else if (result === true) {
-            return StrongPromise.wrap(promise, channelId, location);
+            return StrongPromise.wrap(promise, channelId, caller);
           }
           return response;
         },
       };
 
       MessageChannel.addListener(this.messageManagers, "Extension:Message", listener);
       return () => {
         MessageChannel.removeListener(this.messageManagers, "Extension:Message", listener);

--- a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage.js
@@ -151,20 +151,33 @@ add_task(async function sendMessageRespo
     browser.test.onMessage.addListener(msg => {
       browser.runtime.sendMessage(msg)
         .then(
           response => {
             if (response) {
               browser.test.log(`Got response: ${response}`);
               browser.test.sendMessage(response);
             }
-          }, ({message}) => {
+          }, error => {
+            browser.test.assertEq(
+              "Promised response from onMessage listener went out of scope",
+              error.message,
+              `Promise rejected with the correct error message`);
+
             browser.test.assertTrue(
-              /at background@moz-extension:\/\/[\w-]+\/%7B[\w-]+%7D\.js:4:\d went out/.test(message),
-              `Promise rejected with the correct error message: ${message}`);
+              /^moz-extension:\/\/[\w-]+\/%7B[\w-]+%7D\.js/.test(error.fileName),
+              `Promise rejected with the correct error filename: ${error.fileName}`);
+
+            browser.test.assertEq(
+              4, error.lineNumber,
+              `Promise rejected with the correct error line number`);
+
+            browser.test.assertTrue(
+              /moz-extension:\/\/[\w-]+\/%7B[\w-]+%7D\.js:4/.test(error.stack),
+              `Promise rejected with the correct error stack: ${error.stack}`);
             browser.test.sendMessage("rejected");
           });
     });
     browser.test.sendMessage("ready");
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     background,