diff --git a/src/math/Box3.js b/src/math/Box3.js
index 8784d7b2aedd88..2446efda45e79a 100644
--- a/src/math/Box3.js
+++ b/src/math/Box3.js
@@ -1,5 +1,6 @@
 import { Vector3 } from './Vector3.js';
 import { Sphere } from './Sphere.js';
+import { Matrix4 } from './Matrix4.js';
 
 /**
  * @author bhouston / http://clara.io
@@ -165,13 +166,6 @@ Object.assign( Box3.prototype, {
 
 	getCenter: function ( target ) {
 
-		if ( target === undefined ) {
-
-			console.warn( 'THREE.Box3: .getCenter() target is now required' );
-			target = new Vector3();
-
-		}
-
 		return this.isEmpty() ? target.set( 0, 0, 0 ) : target.addVectors( this.min, this.max ).multiplyScalar( 0.5 );
 
 	},
@@ -384,7 +378,7 @@ Object.assign( Box3.prototype, {
 
 		}
 
-		return ( min <= plane.constant && max >= plane.constant );
+		return ( min <= - plane.constant && max >= - plane.constant );
 
 	},
 
@@ -613,4 +607,4 @@ Object.assign( Box3.prototype, {
 } );
 
 
-export { Box3 };
+export { Box3 };
\ No newline at end of file