--- a/toolkit/components/extensions/ExtensionCommon.jsm
+++ b/toolkit/components/extensions/ExtensionCommon.jsm
@@ -826,28 +826,32 @@ class CanOfAPIs {
   findAPIPath(path) {
     if (this.apiPaths.has(path)) {
       return this.apiPaths.get(path);
     }
 
     let obj = this.root;
     let modules = this.apiManager.modulePaths;
 
-    for (let key of path.split(".")) {
+    let parts = path.split(".");
+    for (let [i, key] of parts.entries()) {
       if (!obj) {
         return;
       }
       modules = getChild(modules, key);
 
       for (let name of modules.modules) {
         if (!this.apis.has(name)) {
           this.loadAPI(name);
         }
       }
 
+      if (!(key in obj) && i < parts.length - 1) {
+        obj[key] = {};
+      }
       obj = obj[key];
     }
 
     this.apiPaths.set(path, obj);
     return obj;
   }
 
   /**
@@ -862,28 +866,33 @@ class CanOfAPIs {
   async asyncFindAPIPath(path) {
     if (this.apiPaths.has(path)) {
       return this.apiPaths.get(path);
     }
 
     let obj = this.root;
     let modules = this.apiManager.modulePaths;
 
-    for (let key of path.split(".")) {
+    let parts = path.split(".");
+    for (let [i, key] of parts.entries()) {
       if (!obj) {
         return;
       }
       modules = getChild(modules, key);
 
       for (let name of modules.modules) {
         if (!this.apis.has(name)) {
           await this.asyncLoadAPI(name);
         }
       }
 
+      if (!(key in obj) && i < parts.length - 1) {
+        obj[key] = {};
+      }
+
       if (typeof obj[key] === "function") {
         obj = obj[key].bind(obj);
       } else {
         obj = obj[key];
       }
     }
 
     this.apiPaths.set(path, obj);