diff --git a/devtools/client/shared/thread-utils.js b/devtools/client/shared/thread-utils.js
index 9c29681b91d3..7f3aa4a8ac54 100644
--- a/devtools/client/shared/thread-utils.js
+++ b/devtools/client/shared/thread-utils.js
@@ -4,8 +4,9 @@
 "use strict";
 
 const asyncStoreHelper = require("resource://devtools/client/shared/async-store-helper.js");
-const { validateBreakpointLocation } = ChromeUtils.import(
-  "resource://devtools/shared/validate-breakpoint.jsm"
+const { validateBreakpointLocation } = ChromeUtils.importESModule(
+  "resource://devtools/shared/validate-breakpoint.sys.mjs",
+  { global: "contextual" }
 );
 
 const asyncStore = asyncStoreHelper("debugger", {
diff --git a/devtools/server/actors/blackboxing.js b/devtools/server/actors/blackboxing.js
index 49dfc8180d5c..8163327b46af 100644
--- a/devtools/server/actors/blackboxing.js
+++ b/devtools/server/actors/blackboxing.js
@@ -9,9 +9,10 @@ const {
   blackboxingSpec,
 } = require("resource://devtools/shared/specs/blackboxing.js");
 
-const {
-  SessionDataHelpers,
-} = require("resource://devtools/server/actors/watcher/SessionDataHelpers.jsm");
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
+);
 const { SUPPORTED_DATA } = SessionDataHelpers;
 const { BLACKBOXING } = SUPPORTED_DATA;
 
diff --git a/devtools/server/actors/breakpoint-list.js b/devtools/server/actors/breakpoint-list.js
index 1f9d6c0bf9e7..a28ffc3f7a0d 100644
--- a/devtools/server/actors/breakpoint-list.js
+++ b/devtools/server/actors/breakpoint-list.js
@@ -9,9 +9,10 @@ const {
   breakpointListSpec,
 } = require("resource://devtools/shared/specs/breakpoint-list.js");
 
-const {
-  SessionDataHelpers,
-} = require("resource://devtools/server/actors/watcher/SessionDataHelpers.jsm");
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
+);
 const { SUPPORTED_DATA } = SessionDataHelpers;
 const { BREAKPOINTS, XHR_BREAKPOINTS, EVENT_BREAKPOINTS } = SUPPORTED_DATA;
 
diff --git a/devtools/server/actors/target-configuration.js b/devtools/server/actors/target-configuration.js
index b6db235143bd..3fec5f4189df 100644
--- a/devtools/server/actors/target-configuration.js
+++ b/devtools/server/actors/target-configuration.js
@@ -9,9 +9,10 @@ const {
   targetConfigurationSpec,
 } = require("resource://devtools/shared/specs/target-configuration.js");
 
-const {
-  SessionDataHelpers,
-} = require("resource://devtools/server/actors/watcher/SessionDataHelpers.jsm");
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
+);
 const { isBrowsingContextPartOfContext } = ChromeUtils.importESModule(
   "resource://devtools/server/actors/watcher/browsing-context-helpers.sys.mjs",
   { global: "contextual" }
diff --git a/devtools/server/actors/targets/session-data-processors/index.js b/devtools/server/actors/targets/session-data-processors/index.js
index 19b7d6930261..72bc769dd146 100644
--- a/devtools/server/actors/targets/session-data-processors/index.js
+++ b/devtools/server/actors/targets/session-data-processors/index.js
@@ -4,9 +4,10 @@
 
 "use strict";
 
-const {
-  SessionDataHelpers,
-} = require("resource://devtools/server/actors/watcher/SessionDataHelpers.jsm");
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
+);
 const { SUPPORTED_DATA } = SessionDataHelpers;
 
 const SessionDataProcessors = {};
diff --git a/devtools/server/actors/thread-configuration.js b/devtools/server/actors/thread-configuration.js
index f0c697bb5106..d3b7e229bfbc 100644
--- a/devtools/server/actors/thread-configuration.js
+++ b/devtools/server/actors/thread-configuration.js
@@ -9,9 +9,10 @@ const {
   threadConfigurationSpec,
 } = require("resource://devtools/shared/specs/thread-configuration.js");
 
-const {
-  SessionDataHelpers,
-} = require("resource://devtools/server/actors/watcher/SessionDataHelpers.jsm");
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
+);
 const {
   SUPPORTED_DATA: { THREAD_CONFIGURATION },
 } = SessionDataHelpers;
diff --git a/devtools/server/actors/watcher/SessionDataHelpers.jsm b/devtools/server/actors/watcher/SessionDataHelpers.sys.mjs
similarity index 82%
rename from devtools/server/actors/watcher/SessionDataHelpers.jsm
rename to devtools/server/actors/watcher/SessionDataHelpers.sys.mjs
index c70df1744f00..4d55ce8d7587 100644
--- a/devtools/server/actors/watcher/SessionDataHelpers.jsm
+++ b/devtools/server/actors/watcher/SessionDataHelpers.sys.mjs
@@ -2,49 +2,30 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-"use strict";
-
 /**
  * Helper module alongside WatcherRegistry, which focus on updating the "sessionData" object.
  * This object is shared across processes and threads and have to be maintained in all these runtimes.
  */
 
-var EXPORTED_SYMBOLS = ["SessionDataHelpers"];
-
 const lazy = {};
+ChromeUtils.defineESModuleGetters(
+  lazy,
+  {
+    validateBreakpointLocation:
+      "resource://devtools/shared/validate-breakpoint.sys.mjs",
+  },
+  { global: "contextual" }
+);
 
-if (typeof module == "object") {
-  // Allow this JSM to also be loaded as a CommonJS module
-  // Because this module is used from the worker thread,
-  // (via target-actor-mixin), and workers can't load JSMs via ChromeUtils.import.
-  loader.lazyRequireGetter(
-    lazy,
-    "validateBreakpointLocation",
-    "resource://devtools/shared/validate-breakpoint.jsm",
-    true
+ChromeUtils.defineLazyGetter(lazy, "validateEventBreakpoint", () => {
+  const { loader } = ChromeUtils.importESModule(
+    "resource://devtools/shared/loader/Loader.sys.mjs",
+    { global: "contextual" }
   );
-
-  loader.lazyRequireGetter(
-    lazy,
-    "validateEventBreakpoint",
-    "resource://devtools/server/actors/utils/event-breakpoints.js",
-    true
-  );
-} else {
-  ChromeUtils.defineLazyGetter(lazy, "validateBreakpointLocation", () => {
-    return ChromeUtils.import(
-      "resource://devtools/shared/validate-breakpoint.jsm"
-    ).validateBreakpointLocation;
-  });
-  ChromeUtils.defineLazyGetter(lazy, "validateEventBreakpoint", () => {
-    const { loader } = ChromeUtils.importESModule(
-      "resource://devtools/shared/loader/Loader.sys.mjs"
-    );
-    return loader.require(
-      "resource://devtools/server/actors/utils/event-breakpoints.js"
-    ).validateEventBreakpoint;
-  });
-}
+  return loader.require(
+    "resource://devtools/server/actors/utils/event-breakpoints.js"
+  ).validateEventBreakpoint;
+});
 
 // List of all arrays stored in `sessionData`, which are replicated across processes and threads
 const SUPPORTED_DATA = {
@@ -151,7 +132,7 @@ function idFunction(v) {
   return v;
 }
 
-const SessionDataHelpers = {
+export const SessionDataHelpers = {
   SUPPORTED_DATA,
 
   /**
@@ -235,10 +216,3 @@ const SessionDataHelpers = {
     return true;
   },
 };
-
-// Allow this JSM to also be loaded as a CommonJS module
-// Because this module is used from the worker thread,
-// (via target-actor-mixin), and workers can't load JSMs.
-if (typeof module == "object") {
-  module.exports.SessionDataHelpers = SessionDataHelpers;
-}
diff --git a/devtools/server/actors/watcher/WatcherRegistry.sys.mjs b/devtools/server/actors/watcher/WatcherRegistry.sys.mjs
index b9693c60f5bb..b177cebb59b4 100644
--- a/devtools/server/actors/watcher/WatcherRegistry.sys.mjs
+++ b/devtools/server/actors/watcher/WatcherRegistry.sys.mjs
@@ -26,8 +26,9 @@
 
 import { ActorManagerParent } from "resource://gre/modules/ActorManagerParent.sys.mjs";
 
-const { SessionDataHelpers } = ChromeUtils.import(
-  "resource://devtools/server/actors/watcher/SessionDataHelpers.jsm"
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
 );
 
 const { SUPPORTED_DATA } = SessionDataHelpers;
diff --git a/devtools/server/actors/watcher/moz.build b/devtools/server/actors/watcher/moz.build
index 46a9d897187e..27674a2dc045 100644
--- a/devtools/server/actors/watcher/moz.build
+++ b/devtools/server/actors/watcher/moz.build
@@ -11,6 +11,6 @@ DIRS += [
 DevToolsModules(
     "browsing-context-helpers.sys.mjs",
     "session-context.js",
-    "SessionDataHelpers.jsm",
+    "SessionDataHelpers.sys.mjs",
     "WatcherRegistry.sys.mjs",
 )
diff --git a/devtools/server/connectors/js-window-actor/DevToolsWorkerChild.sys.mjs b/devtools/server/connectors/js-window-actor/DevToolsWorkerChild.sys.mjs
index 6bbe4140c326..e864356d0861 100644
--- a/devtools/server/connectors/js-window-actor/DevToolsWorkerChild.sys.mjs
+++ b/devtools/server/connectors/js-window-actor/DevToolsWorkerChild.sys.mjs
@@ -22,13 +22,11 @@ ChromeUtils.defineLazyGetter(lazy, "Loader", () =>
 ChromeUtils.defineLazyGetter(lazy, "DevToolsUtils", () =>
   lazy.Loader.require("resource://devtools/shared/DevToolsUtils.js")
 );
-XPCOMUtils.defineLazyModuleGetters(lazy, {
-  SessionDataHelpers:
-    "resource://devtools/server/actors/watcher/SessionDataHelpers.jsm",
-});
 ChromeUtils.defineESModuleGetters(lazy, {
   isWindowGlobalPartOfContext:
     "resource://devtools/server/actors/watcher/browsing-context-helpers.sys.mjs",
+  SessionDataHelpers:
+    "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
 });
 
 // Name of the attribute into which we save data in `sharedData` object.
diff --git a/devtools/server/connectors/process-actor/DevToolsServiceWorkerChild.sys.mjs b/devtools/server/connectors/process-actor/DevToolsServiceWorkerChild.sys.mjs
index 62232f483df4..28e9c73c4369 100644
--- a/devtools/server/connectors/process-actor/DevToolsServiceWorkerChild.sys.mjs
+++ b/devtools/server/connectors/process-actor/DevToolsServiceWorkerChild.sys.mjs
@@ -8,6 +8,8 @@ import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 const lazy = {};
 ChromeUtils.defineESModuleGetters(lazy, {
   loader: "resource://devtools/shared/loader/Loader.sys.mjs",
+  SessionDataHelpers:
+    "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
 });
 
 XPCOMUtils.defineLazyServiceGetter(
@@ -17,11 +19,6 @@ XPCOMUtils.defineLazyServiceGetter(
   "nsIWorkerDebuggerManager"
 );
 
-XPCOMUtils.defineLazyModuleGetters(lazy, {
-  SessionDataHelpers:
-    "resource://devtools/server/actors/watcher/SessionDataHelpers.jsm",
-});
-
 ChromeUtils.defineLazyGetter(lazy, "DevToolsUtils", () =>
   lazy.loader.require("devtools/shared/DevToolsUtils")
 );
diff --git a/devtools/server/tests/xpcshell/test_sessionDataHelpers.js b/devtools/server/tests/xpcshell/test_sessionDataHelpers.js
index e0dcc3b21b7e..0c17937a693c 100644
--- a/devtools/server/tests/xpcshell/test_sessionDataHelpers.js
+++ b/devtools/server/tests/xpcshell/test_sessionDataHelpers.js
@@ -7,8 +7,9 @@
 
 "use strict";
 
-const { SessionDataHelpers } = ChromeUtils.import(
-  "resource://devtools/server/actors/watcher/SessionDataHelpers.jsm"
+const { SessionDataHelpers } = ChromeUtils.importESModule(
+  "resource://devtools/server/actors/watcher/SessionDataHelpers.sys.mjs",
+  { global: "contextual" }
 );
 const { SUPPORTED_DATA } = SessionDataHelpers;
 const { TARGETS } = SUPPORTED_DATA;
diff --git a/devtools/shared/loader/worker-loader.js b/devtools/shared/loader/worker-loader.js
index d69ddd9d23f8..eee2b96d67f6 100644
--- a/devtools/shared/loader/worker-loader.js
+++ b/devtools/shared/loader/worker-loader.js
@@ -173,9 +173,7 @@ function WorkerDebuggerLoader(options) {
     }
 
     // If the url has no extension, use ".js" by default.
-    // Also allow loading JSMs, but they would need a shim in order to
-    // be loaded as a CommonJS module. (See SessionDataHelpers.jsm)
-    return url.endsWith(".js") || url.endsWith(".jsm") ? url : url + ".js";
+    return url.endsWith(".js") ? url : url + ".js";
   }
 
   /**
diff --git a/devtools/shared/moz.build b/devtools/shared/moz.build
index 55243817410e..9fa41cfc4010 100644
--- a/devtools/shared/moz.build
+++ b/devtools/shared/moz.build
@@ -71,7 +71,7 @@ DevToolsModules(
     "system.js",
     "ThreadSafeDevToolsUtils.js",
     "throttle.js",
-    "validate-breakpoint.jsm",
+    "validate-breakpoint.sys.mjs",
 )
 
 with Files("**"):
diff --git a/devtools/shared/validate-breakpoint.jsm b/devtools/shared/validate-breakpoint.sys.mjs
similarity index 69%
rename from devtools/shared/validate-breakpoint.jsm
rename to devtools/shared/validate-breakpoint.sys.mjs
index b065ead7aaa8..b555355ce7b9 100644
--- a/devtools/shared/validate-breakpoint.jsm
+++ b/devtools/shared/validate-breakpoint.sys.mjs
@@ -2,17 +2,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-"use strict";
-
-// Because this function is used from SessionDataHelpers.jsm,
-// this has to be a JSM.
-
-var EXPORTED_SYMBOLS = ["validateBreakpointLocation"];
-
 /**
  * Given a breakpoint location object, throws if the breakpoint look invalid
  */
-function validateBreakpointLocation({ sourceUrl, sourceId, line, column }) {
+export function validateBreakpointLocation({
+  sourceUrl,
+  sourceId,
+  line,
+  column,
+}) {
   if (!sourceUrl && !sourceId) {
     throw new Error(
       `Breakpoints expect to have either a sourceUrl or a sourceId.`
@@ -40,10 +38,3 @@ function validateBreakpointLocation({ sourceUrl, sourceId, line, column }) {
     );
   }
 }
-
-// Allow this JSM to also be loaded as a CommonJS module
-// Because this module is used from the worker thread,
-// and workers can't load JSMs.
-if (typeof module == "object") {
-  module.exports.validateBreakpointLocation = validateBreakpointLocation;
-}