diff --git a/.eslintrc.json b/.eslintrc.json
index c4a67231b..e0e705f21 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -42,7 +42,7 @@
         "no-console": "error",
         "compat/compat": [
           "error",
-          "android >= 4.3, firefox >= 45, ie >= 11, safari >= 9.1, ios_saf >= 7, chrome >= 58"
+          "android >= 4.3, firefox >= 45, ie >= 9, safari >= 9.1, ios_saf >= 7, chrome >= 58"
         ]
       }
     },
@@ -61,7 +61,7 @@
       "rules": {
         "compat/compat": [
           "error",
-          "android >= 4.3, firefox >= 45, ie >= 11, safari >= 9.1, chrome >= 58"
+          "android >= 4.3, firefox >= 45, ie >= 9, safari >= 9.1, chrome >= 58"
         ],
         "max-len": "off",
         "no-throw-literal": "off",
diff --git a/History.md b/History.md
index bc3c09ddc..cafeb5241 100644
--- a/History.md
+++ b/History.md
@@ -48,8 +48,7 @@ QUnit 3.0 Roadmap and feedback: https://github.com/qunitjs/qunit/issues/1498
 ### Removed
 
 * Core: Remove support for Node.js 10-16. Node.js 18 or later is required. [#1727](https://github.com/qunitjs/qunit/issues/1727)
-* Core: Remove support for IE 9 and IE 10. IE 11 remains supported. [#1725](https://github.com/qunitjs/qunit/issues/1725)
-* Core: Remove support for PhantomJS.
+* Core: Remove support for PhantomJS. (Steve McClure) [#1505](https://github.com/qunitjs/qunit/pull/1505)
 * Core: Remove built-in export for AMD. You can still load your application and your QUnit tests with AMD/RequireJS. This only affects the loading of the qunit.js file itself. [Example: Loading with RequireJS](https://qunitjs.com/api/config/autostart/#loading-with-requirejs). (NullVoxPopuli) [#1729](https://github.com/qunitjs/qunit/issues/1729)
 * Core: Remove deprecated [`QUnit.load()`](https://qunitjs.com/api/QUnit/load/). [#1084](https://github.com/qunitjs/qunit/issues/1084)
 * Core: Remove deprecated `QUnit.onError()` and `QUnit.onUnhandledRejection()` in favor of [QUnit.onUncaughtException()](https://qunitjs.com/api/extension/QUnit.onUncaughtException/).
@@ -355,7 +354,7 @@ QUnit 3.0 Roadmap and feedback: https://github.com/qunitjs/qunit/issues/1498
 
 ### Deprecated
 
-* HTML Reporter: Deprecate PhantomJS. (Steve McClure)
+* HTML Reporter: Deprecate PhantomJS. (Steve McClure) [#1505](https://github.com/qunitjs/qunit/pull/1505)
 
 ### Fixed
 
diff --git a/build/browserstack-full.json b/build/browserstack-full.json
index de4ad9aaf..87cd3583c 100644
--- a/build/browserstack-full.json
+++ b/build/browserstack-full.json
@@ -9,6 +9,8 @@
     "firefox_78",
     "firefox_previous",
     "firefox_current",
+    "ie_9",
+    "ie_10",
     "ie_11",
     "edge_15",
     "edge_18",
diff --git a/build/browserstack-quick.json b/build/browserstack-quick.json
index 580d60b35..f74dc4f8d 100644
--- a/build/browserstack-quick.json
+++ b/build/browserstack-quick.json
@@ -7,7 +7,7 @@
   "browsers": [
     "firefox_45",
     "firefox_current",
-    "ie_11",
+    "ie_9",
     "safari_9.1",
     "safari_current",
     "opera_current",
diff --git a/src/core/globals.js b/src/core/globals.js
index be1b24bba..c0fc7a83a 100644
--- a/src/core/globals.js
+++ b/src/core/globals.js
@@ -65,7 +65,7 @@ export const sessionStorage = (function () {
 
 // Fallback for ES6 Map, `new Map(iterable)`, and ES7 Map#keys
 //
-// Support: Safari 7; Map is undefined
+// Support: IE 9-11, iOS 7; Map is undefined
 // Support: iOS 8; `new Map(iterable)` is not supported
 // Support: IE 11; Map#keys is undefined
 export const StringMap = typeof g.Map === 'function'
diff --git a/src/core/logger.js b/src/core/logger.js
index 0ab042d3b..6bef60b7b 100644
--- a/src/core/logger.js
+++ b/src/core/logger.js
@@ -1,10 +1,14 @@
 import { console } from './globals.js';
 
+// Support IE 9: No console object, unless the developer tools are not open.
+
+// Support IE 9: Function#bind is supported, but no console.log.bind().
+
 // Support: SpiderMonkey (mozjs 68+)
 // The console object has a log method, but no warn method.
 
 export default {
   warn: console
-    ? (console.warn || console.log).bind(console)
+    ? Function.prototype.bind.call(console.warn || console.log, console)
     : function () {}
 };
diff --git a/src/core/reporters/ConsoleReporter.js b/src/core/reporters/ConsoleReporter.js
index edf00ce3a..1e22678cb 100644
--- a/src/core/reporters/ConsoleReporter.js
+++ b/src/core/reporters/ConsoleReporter.js
@@ -5,7 +5,8 @@ export default class ConsoleReporter {
     // Cache references to console methods to ensure we can report failures
     // from tests tests that mock the console object itself.
     // https://github.com/qunitjs/qunit/issues/1340
-    this.log = options.log || console.log.bind(console);
+    // Support IE 9: Function#bind is supported, but no console.log.bind().
+    this.log = options.log || Function.prototype.bind.call(console.log, console);
 
     runner.on('error', this.onError.bind(this));
     runner.on('runStart', this.onRunStart.bind(this));
diff --git a/src/core/reporters/HtmlReporter.js b/src/core/reporters/HtmlReporter.js
index 0d96e7b5e..7793f8a40 100644
--- a/src/core/reporters/HtmlReporter.js
+++ b/src/core/reporters/HtmlReporter.js
@@ -47,10 +47,18 @@ const DOM = {
     }
 
     // Trim for prettiness
-    elem.className = set.trim();
+    elem.className = trim(set);
   }
 };
 
+function trim (string) {
+  if (typeof string.trim === 'function') {
+    return string.trim();
+  } else {
+    return string.replace(/^\s+|\s+$/g, '');
+  }
+}
+
 function stripHtml (string) {
   // Strip tags, html entity and whitespaces
   return string
@@ -177,7 +185,7 @@ export default class HtmlReporter {
   onFilterSubmit (ev) {
     // Trim potential accidental whitespace so that QUnit doesn't throw an error about no tests matching the filter.
     const filterInputElem = this.element.querySelector('#qunit-filter-input');
-    filterInputElem.value = filterInputElem.value.trim();
+    filterInputElem.value = trim(filterInputElem.value);
 
     this.applyUrlParams();
 
diff --git a/src/core/reporters/TapReporter.js b/src/core/reporters/TapReporter.js
index e4f3aa183..dbce65ee6 100644
--- a/src/core/reporters/TapReporter.js
+++ b/src/core/reporters/TapReporter.js
@@ -42,7 +42,7 @@ function prettyYamlValue (value, indent = 4) {
     value = String(value);
   }
 
-  // Support IE 11: Use isFinite instead of ES6 Number.isFinite
+  // Support IE 9-11: Use isFinite instead of ES6 Number.isFinite
   if (typeof value === 'number' && !isFinite(value)) {
     // Turn NaN and Infinity into simple strings.
     // Paranoia: Don't return directly just in case there's
@@ -93,7 +93,7 @@ function prettyYamlValue (value, indent = 4) {
       }
 
       // See also <https://yaml-multiline.info/>
-      // Support IE 11: Avoid ES6 String#repeat
+      // Support IE 9-11: Avoid ES6 String#repeat
       const prefix = (new Array(indent + 1)).join(' ');
 
       const trailingLinebreakMatch = value.match(/\n+$/);
@@ -174,7 +174,8 @@ export default class TapReporter {
     // Cache references to console methods to ensure we can report failures
     // from tests tests that mock the console object itself.
     // https://github.com/qunitjs/qunit/issues/1340
-    this.log = options.log || console.log.bind(console);
+    // Support IE 9: Function#bind is supported, but no console.log.bind().
+    this.log = options.log || Function.prototype.bind.call(console.log, console);
 
     this.testCount = 0;
     this.started = false;
diff --git a/src/core/stacktrace.js b/src/core/stacktrace.js
index 4dfac41dd..0e33a0dd5 100644
--- a/src/core/stacktrace.js
+++ b/src/core/stacktrace.js
@@ -36,7 +36,7 @@ function qunitFileName () {
   let error = new Error();
   if (!error.stack) {
     // Copy of sourceFromStacktrace() to avoid circular dependency
-    // Support: IE 11
+    // Support: IE 9-11
     try {
       throw error;
     } catch (err) {
@@ -83,7 +83,7 @@ export function annotateStacktrace (stack, formatInternal, eToString = null) {
   let initialInternal = true;
   for (let i = 0; i < frames.length; i++) {
     const frame = frames[i];
-    const isInternal = (frame.indexOf(fileName) !== -1 || frame.indexOf('node:internal/') !== -1);
+    const isInternal = ((fileName && frame.indexOf(fileName) !== -1) || frame.indexOf('node:internal/') !== -1);
     if (!isInternal) {
       initialInternal = false;
     }
@@ -127,7 +127,7 @@ export function extractStacktrace (e, offset) {
 export function sourceFromStacktrace (offset) {
   let error = new Error();
 
-  // Support: IE 11, iOS 7
+  // Support: IE 9-11, iOS 7
   // Not all browsers generate the `stack` property for `new Error()`
   // See also https://github.com/qunitjs/qunit/issues/636
   if (!error.stack) {
diff --git a/test/main/promise.js b/test/main/promise.js
index 0c16ef996..1d39e8e6a 100644
--- a/test/main/promise.js
+++ b/test/main/promise.js
@@ -1,3 +1,4 @@
+// Support IE 9: Promise not supported.
 // Support SpiderMonkey: setTimeout is not supported, but native Promise is.
 var defer = typeof setTimeout !== 'undefined'
   // eslint-disable-next-line no-undef
diff --git a/test/webWorker.js b/test/webWorker.js
index e49f3c597..58bf41a9e 100644
--- a/test/webWorker.js
+++ b/test/webWorker.js
@@ -4,6 +4,7 @@ QUnit.module('Web Worker');
 QUnit.test('main tests', function (assert) {
   assert.timeout(10000);
   var done = assert.async();
+  // eslint-disable-next-line compat/compat -- Test skipped in IE9
   var worker = new Worker('webWorker-worker.js');
 
   worker.onmessage = function (event) {