diff --git a/src/js/mods/mod_interface.js b/src/js/mods/mod_interface.js
index ab6b4077..3f61fce1 100644
--- a/src/js/mods/mod_interface.js
+++ b/src/js/mods/mod_interface.js
@@ -391,11 +391,11 @@ export class ModInterface {
 
     /**
      *
-     * @param {typeof Object} classHandle
+     * @param {Object} obj
      * @param {({ $super, $old }) => any} extender
      */
-    extendClass(classHandle, extender) {
-        const prototype = classHandle.prototype;
+    extendObject(obj, extender) {
+        const prototype = obj.prototype;
 
         const $super = Object.getPrototypeOf(prototype);
         const $old = {};
@@ -409,4 +409,13 @@ export class ModInterface {
             prototype[propertyName] = extensionMethods[propertyName];
         });
     }
+
+    /**
+     *
+     * @param {typeof Object} classHandle
+     * @param {({ $super, $old }) => any} extender
+     */
+    extendClass(classHandle, extender) {
+        this.extendObject(classHandle.prototype, extender);
+    }
 }
diff --git a/src/js/mods/modloader.js b/src/js/mods/modloader.js
index 668411f3..fa90b8a6 100644
--- a/src/js/mods/modloader.js
+++ b/src/js/mods/modloader.js
@@ -121,6 +121,9 @@ export class ModLoader {
         }
 
         window.$shapez_registerMod = (modClass, meta) => {
+            if (this.initialized) {
+                throw new Error("Can't register mod after modloader is initialized");
+            }
             if (this.modLoadQueue.some(entry => entry.meta.id === meta.id)) {
                 console.warn("Not registering mod", meta, "since a mod with the same id is already loaded");
                 return;
@@ -151,8 +154,6 @@ export class ModLoader {
 
         delete window.$shapez_registerMod;
 
-        this.initialized = true;
-
         for (let i = 0; i < this.modLoadQueue.length; i++) {
             const { modClass, meta } = this.modLoadQueue[i];
             const modDataFile = "modsettings_" + meta.id + "__" + meta.version + ".json";
@@ -190,6 +191,7 @@ export class ModLoader {
         }
 
         this.modLoadQueue = [];
+        this.initialized = true;
     }
 }