diff --git a/common/content/buffer.js b/common/content/buffer.js
index 1642f3118..2cf6277d9 100644
--- a/common/content/buffer.js
+++ b/common/content/buffer.js
@@ -1814,6 +1814,9 @@ const Buffer = Module("buffer", {
 });
 
 /* Expose Buffer constructor */
-Object.defineProperty(this, "Buffer", { value: Buffer });
+Object.defineProperty(modules, "Buffer", {
+    value: Buffer,
+    enumerable: true
+});
 
 // vim: set fdm=marker sw=4 ts=4 et:
diff --git a/common/content/commands.js b/common/content/commands.js
index 45dcd7fca..388cb4726 100644
--- a/common/content/commands.js
+++ b/common/content/commands.js
@@ -1188,7 +1188,10 @@ const Commands = Module("commands", {
 
 (function () {
     /* Expose Command constructor for user-defined sub-commands. */
-    Object.defineProperty(this, "Command", { value: Command });
+    Object.defineProperty(modules, "Command", {
+        value: Command,
+        enumerable: true
+    });
 
     Commands.quoteMap = {
         "\n": "n",