diff --git a/src/math/Matrix3.js b/src/math/Matrix3.js
index 5446270579e55b0ece5d538792c983075e93ff9b..1631c7d57cb7a156001696da4ccdb91ca6862e57 100644
--- a/src/math/Matrix3.js
+++ b/src/math/Matrix3.js
@@ -66,7 +66,9 @@ Object.assign( Matrix3.prototype, {
 		var te = this.elements;
 		var me = m.elements;
 
-		for ( var i = 0; i < 9; i ++ ) te[ i ] = me[ i ];
+		te[ 0 ] = me[ 0 ]; te[ 1 ] = me[ 1 ]; te[ 2 ] = me[ 2 ];
+		te[ 3 ] = me[ 3 ]; te[ 4 ] = me[ 4 ]; te[ 5 ] = me[ 5 ];
+		te[ 6 ] = me[ 6 ]; te[ 7 ] = me[ 7 ]; te[ 8 ] = me[ 8 ];
 
 		return this;
 
diff --git a/src/math/Matrix4.js b/src/math/Matrix4.js
index f5cc5beb49e620df0a288e2c3a204d6f901617fe..fa3f8b02d785dfda3eed02914db0869c12c61a62 100644
--- a/src/math/Matrix4.js
+++ b/src/math/Matrix4.js
@@ -75,7 +75,10 @@ Object.assign( Matrix4.prototype, {
 		var te = this.elements;
 		var me = m.elements;
 
-		for ( var i = 0; i < 16; i ++ ) te[ i ] = me[ i ];
+		te[ 0 ] = me[ 0 ]; te[ 1 ] = me[ 1 ]; te[ 2 ] = me[ 2 ]; te[ 3 ] = me[ 3 ];
+		te[ 4 ] = me[ 4 ]; te[ 5 ] = me[ 5 ]; te[ 6 ] = me[ 6 ]; te[ 7 ] = me[ 7 ];
+		te[ 8 ] = me[ 8 ]; te[ 9 ] = me[ 9 ]; te[ 10 ] = me[ 10 ]; te[ 11 ] = me[ 11 ];
+		te[ 12 ] = me[ 12 ]; te[ 13 ] = me[ 13 ]; te[ 14 ] = me[ 14 ]; te[ 15 ] = me[ 15 ];
 
 		return this;
 
@@ -764,18 +767,14 @@ Object.assign( Matrix4.prototype, {
 
 			// if determine is negative, we need to invert one scale
 			var det = this.determinant();
-			if ( det < 0 ) {
-
-				sx = - sx;
-
-			}
+			if ( det < 0 ) sx = - sx;
 
 			position.x = te[ 12 ];
 			position.y = te[ 13 ];
 			position.z = te[ 14 ];
 
 			// scale the rotation part
-			for ( var i = 0; i < 16; i ++ ) matrix.elements[ i ] = this.elements[ i ]; // at this point matrix is incomplete so we can't use .copy()
+			matrix.copy( this );
 
 			var invSX = 1 / sx;
 			var invSY = 1 / sy;
@@ -870,7 +869,7 @@ Object.assign( Matrix4.prototype, {
 
 		if ( offset === undefined ) offset = 0;
 
-		for( var i = 0; i < 16; i ++ ) {
+		for ( var i = 0; i < 16; i ++ ) {
 
 			this.elements[ i ] = array[ i + offset ];
 
@@ -897,8 +896,8 @@ Object.assign( Matrix4.prototype, {
 		array[ offset + 6 ] = te[ 6 ];
 		array[ offset + 7 ] = te[ 7 ];
 
-		array[ offset + 8 ]  = te[ 8 ];
-		array[ offset + 9 ]  = te[ 9 ];
+		array[ offset + 8 ] = te[ 8 ];
+		array[ offset + 9 ] = te[ 9 ];
 		array[ offset + 10 ] = te[ 10 ];
 		array[ offset + 11 ] = te[ 11 ];