diff --git a/src/constraint/MouseConstraint.js b/src/constraint/MouseConstraint.js
index acd1d84..7cb0830 100644
--- a/src/constraint/MouseConstraint.js
+++ b/src/constraint/MouseConstraint.js
@@ -31,7 +31,7 @@ var MouseConstraint = {};
             mouse: mouse,
             dragBody: null,
             dragPoint: null,
-            constraints: [constraint]
+            constraint: constraint
         };
     };
 
@@ -43,7 +43,7 @@ var MouseConstraint = {};
      */
     MouseConstraint.update = function(mouseConstraint, bodies) {
         var mouse = mouseConstraint.mouse,
-            constraint = mouseConstraint.constraints[0];
+            constraint = mouseConstraint.constraint;
 
         if (mouse.button === 0 || mouse.button === 2) {
             if (!constraint.bodyB) {
diff --git a/src/core/Engine.js b/src/core/Engine.js
index f77d7c9..bb2f162 100644
--- a/src/core/Engine.js
+++ b/src/core/Engine.js
@@ -71,7 +71,7 @@ var Engine = {};
         engine.metrics = engine.metrics || Metrics.create();
         engine.input.mouse = engine.input.mouse || Mouse.create(engine.render.canvas);
         engine.mouseConstraint = engine.mouseConstraint || MouseConstraint.create(engine.input.mouse);
-        World.addComposite(engine.world, engine.mouseConstraint);
+        World.addConstraint(engine.world, engine.mouseConstraint.constraint);
 
         engine.broadphase = engine.broadphase || {
             current: 'grid',
@@ -340,7 +340,7 @@ var Engine = {};
         engine.pairs.table = {};
         engine.pairs.list = [];
 
-        World.addComposite(engine.world, engine.mouseConstraint);
+        World.addConstraint(engine.world, engine.mouseConstraint.constraint);
 
         var broadphase = engine.broadphase[engine.broadphase.current];