diff --git a/src/core/space.js b/src/core/space.js
index 07f6fb3..0ef9727 100644
--- a/src/core/space.js
+++ b/src/core/space.js
@@ -4,6 +4,19 @@ if ( typeof define !== "function" ) {
 
 define( function( require ) {
 
+  function Space( clock ) {
+    // This will normally be the system simulation clock, but for a UI space
+    // it might be the realtime clock instead.
+    this.clock = new Clock( clock.signal ); // This clock controls updates for
+                                            // all entities in this space
+    this.id = guid();
+    this.size = 0; // The number of entities in this space
+
+    this._entities = {}; // Maps entity ID to object
+    this._nameIndex = {}; // Maps name to entity ID
+    this._tagIndex = {}; // Maps tag to entity ID
+  }
+
   var guid = require( "common/guid" );
   var Entity = require( "core/entity" );
   var Clock = require( "core/clock" );
@@ -147,19 +160,6 @@ define( function( require ) {
     return result;
   }
 
-  function Space( clock ) {
-    // This will normally be the system simulation clock, but for a UI space
-    // it might be the realtime clock instead.
-    this.clock = new Clock( clock.signal ); // This clock controls updates for
-                                            // all entities in this space
-    this.id = guid();
-    this.size = 0; // The number of entities in this space
-
-    this._entities = {}; // Maps entity ID to object
-    this._nameIndex = {}; // Maps name to entity ID
-    this._tagIndex = {}; // Maps tag to entity ID
-  }
-
   Space.prototype = {
       add: add,
       remove: remove,