--- a/devtools/server/connectors/content-process-connector.js
+++ b/devtools/server/connectors/content-process-connector.js
@@ -16,33 +16,28 @@ loader.lazyRequireGetter(
 );
 
 const CONTENT_PROCESS_SERVER_STARTUP_SCRIPT =
   "resource://devtools/server/startup/content-process.js";
 
 loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/event-emitter");
 
 const ContentProcessConnector = {
-  // Flag to check if the content process server startup script was already loaded.
-  _contentProcessServerStartupScriptLoaded: false,
-
   /**
    * Start a DevTools server in a content process (representing the entire process, not
    * just a single frame) and add it as a child server for an active connection.
    */
   startServer(connection, mm, onDestroy) {
     return new Promise(resolve => {
       const prefix = connection.allocID("content-process");
       let actor, childTransport;
 
       mm.addMessageListener("debug:content-process-actor", function listener(
         msg
       ) {
-        // Arbitrarily choose the first content process to reply
-        // XXX: This code needs to be updated if we use more than one content process
         mm.removeMessageListener("debug:content-process-actor", listener);
 
         // Pipe Debugger message from/to parent/child via the message manager
         childTransport = new ChildDebuggerTransport(mm, prefix);
         childTransport.hooks = {
           onPacket: connection.send.bind(connection),
           onClosed() {},
         };
@@ -53,23 +48,25 @@ const ContentProcessConnector = {
         dumpn(`Start forwarding for process with prefix ${prefix}`);
 
         actor = msg.json.actor;
 
         resolve(actor);
       });
 
       // Load the content process server startup script only once.
-      if (!this._contentProcessServerStartupScriptLoaded) {
+      const isContentProcessServerStartupScripLoaded = Services.ppmm
+        .getDelayedProcessScripts()
+        .some(([uri]) => uri === CONTENT_PROCESS_SERVER_STARTUP_SCRIPT);
+      if (!isContentProcessServerStartupScripLoaded) {
         // Load the process script that will receive the debug:init-content-server message
         Services.ppmm.loadProcessScript(
           CONTENT_PROCESS_SERVER_STARTUP_SCRIPT,
           true
         );
-        this._contentProcessServerStartupScriptLoaded = true;
       }
 
       // Send a message to the content process server startup script to forward it the
       // prefix.
       mm.sendAsyncMessage("debug:init-content-server", {
         prefix: prefix,
       });