diff --git a/spine-csharp/src/IkConstraint.cs b/spine-csharp/src/IkConstraint.cs
index c71fb0fa4..bc92980da 100644
--- a/spine-csharp/src/IkConstraint.cs
+++ b/spine-csharp/src/IkConstraint.cs
@@ -52,26 +52,24 @@ namespace Spine {
 		public IkConstraint (IkConstraintData data, Skeleton skeleton) {
 			if (data == null) throw new ArgumentNullException("data", "data cannot be null.");
 			this.data = data;
-			mix = data.mix;
-			softness = data.softness;
-			bendDirection = data.bendDirection;
-			compress = data.compress;
-			stretch = data.stretch;
 
 			bones = new ExposedList<Bone>(data.bones.Count);
 			foreach (BoneData boneData in data.bones)
 				bones.Add(skeleton.bones.Items[boneData.index]);
 
 			target = skeleton.bones.Items[data.target.index];
+
+			mix = data.mix;
+			softness = data.softness;
+			bendDirection = data.bendDirection;
+			compress = data.compress;
+			stretch = data.stretch;
 		}
 
 		/// <summary>Copy constructor.</summary>
-		public IkConstraint (IkConstraint constraint) {
-			if (constraint == null) throw new ArgumentNullException("constraint", "constraint cannot be null.");
-			data = constraint.data;
-			bones = new ExposedList<Bone>(constraint.Bones.Count);
-			bones.AddRange(constraint.Bones);
-			target = constraint.target;
+		public IkConstraint (IkConstraint constraint, Skeleton skeleton)
+			: this(constraint.data, skeleton) {
+
 			mix = constraint.mix;
 			softness = constraint.softness;
 			bendDirection = constraint.bendDirection;
diff --git a/spine-csharp/src/PathConstraint.cs b/spine-csharp/src/PathConstraint.cs
index 6a8c9b775..0a13c45c2 100644
--- a/spine-csharp/src/PathConstraint.cs
+++ b/spine-csharp/src/PathConstraint.cs
@@ -64,6 +64,7 @@ namespace Spine {
 				bones.Add(skeleton.bones.Items[boneData.index]);
 
 			target = skeleton.slots.Items[data.target.index];
+
 			position = data.position;
 			spacing = data.spacing;
 			mixRotate = data.mixRotate;
@@ -72,12 +73,9 @@ namespace Spine {
 		}
 
 		/// <summary>Copy constructor.</summary>
-		public PathConstraint (PathConstraint constraint) {
-			if (constraint == null) throw new ArgumentNullException("constraint cannot be null.");
-			data = constraint.data;
-			bones = new ExposedList<Bone>(constraint.Bones.Count);
-			bones.AddRange(constraint.Bones);
-			target = constraint.target;
+		public PathConstraint (PathConstraint constraint, Skeleton skeleton)
+			: this(constraint.data, skeleton) {
+
 			position = constraint.position;
 			spacing = constraint.spacing;
 			mixRotate = constraint.mixRotate;
diff --git a/spine-csharp/src/PhysicsConstraint.cs b/spine-csharp/src/PhysicsConstraint.cs
index aede953ec..4221b0aec 100644
--- a/spine-csharp/src/PhysicsConstraint.cs
+++ b/spine-csharp/src/PhysicsConstraint.cs
@@ -60,7 +60,9 @@ namespace Spine {
 			if (skeleton == null) throw new ArgumentNullException("skeleton", "skeleton cannot be null.");
 			this.data = data;
 			this.skeleton = skeleton;
+
 			bone = skeleton.bones.Items[data.bone.index];
+
 			inertia = data.inertia;
 			strength = data.strength;
 			damping = data.damping;
@@ -71,11 +73,9 @@ namespace Spine {
 		}
 
 		/// <summary>Copy constructor.</summary>
-		public PhysicsConstraint (PhysicsConstraint constraint) {
-			if (constraint == null) throw new ArgumentNullException("constraint", "constraint cannot be null.");
-			data = constraint.data;
-			skeleton = constraint.skeleton;
-			bone = constraint.bone;
+		public PhysicsConstraint (PhysicsConstraint constraint, Skeleton skeleton)
+			: this(constraint.data, skeleton) {
+
 			inertia = constraint.inertia;
 			strength = constraint.strength;
 			damping = constraint.damping;
diff --git a/spine-csharp/src/Skeleton.cs b/spine-csharp/src/Skeleton.cs
index 774e2472b..522b27fc6 100644
--- a/spine-csharp/src/Skeleton.cs
+++ b/spine-csharp/src/Skeleton.cs
@@ -187,19 +187,19 @@ namespace Spine {
 
 			ikConstraints = new ExposedList<IkConstraint>(skeleton.ikConstraints.Count);
 			foreach (IkConstraint ikConstraint in skeleton.ikConstraints)
-				ikConstraints.Add(new IkConstraint(ikConstraint));
+				ikConstraints.Add(new IkConstraint(ikConstraint, skeleton));
 
 			transformConstraints = new ExposedList<TransformConstraint>(skeleton.transformConstraints.Count);
 			foreach (TransformConstraint transformConstraint in skeleton.transformConstraints)
-				transformConstraints.Add(new TransformConstraint(transformConstraint));
+				transformConstraints.Add(new TransformConstraint(transformConstraint, skeleton));
 
 			pathConstraints = new ExposedList<PathConstraint>(skeleton.pathConstraints.Count);
 			foreach (PathConstraint pathConstraint in skeleton.pathConstraints)
-				pathConstraints.Add(new PathConstraint(pathConstraint));
+				pathConstraints.Add(new PathConstraint(pathConstraint, skeleton));
 
 			physicsConstraints = new ExposedList<PhysicsConstraint>(skeleton.physicsConstraints.Count);
 			foreach (PhysicsConstraint physicsConstraint in skeleton.physicsConstraints)
-				physicsConstraints.Add(new PhysicsConstraint(physicsConstraint));
+				physicsConstraints.Add(new PhysicsConstraint(physicsConstraint, skeleton));
 
 			skin = skeleton.skin;
 			r = skeleton.r;
diff --git a/spine-csharp/src/TransformConstraint.cs b/spine-csharp/src/TransformConstraint.cs
index e234de305..2d50fc210 100644
--- a/spine-csharp/src/TransformConstraint.cs
+++ b/spine-csharp/src/TransformConstraint.cs
@@ -51,27 +51,25 @@ namespace Spine {
 			if (data == null) throw new ArgumentNullException("data", "data cannot be null.");
 			if (skeleton == null) throw new ArgumentNullException("skeleton", "skeleton cannot be null.");
 			this.data = data;
-			mixRotate = data.mixRotate;
-			mixX = data.mixX;
-			mixY = data.mixY;
-			mixScaleX = data.mixScaleX;
-			mixScaleY = data.mixScaleY;
-			mixShearY = data.mixShearY;
 
 			bones = new ExposedList<Bone>();
 			foreach (BoneData boneData in data.bones)
 				bones.Add(skeleton.bones.Items[boneData.index]);
 
 			target = skeleton.bones.Items[data.target.index];
+
+			mixRotate = data.mixRotate;
+			mixX = data.mixX;
+			mixY = data.mixY;
+			mixScaleX = data.mixScaleX;
+			mixScaleY = data.mixScaleY;
+			mixShearY = data.mixShearY;
 		}
 
 		/// <summary>Copy constructor.</summary>
-		public TransformConstraint (TransformConstraint constraint) {
-			if (constraint == null) throw new ArgumentNullException("constraint cannot be null.");
-			data = constraint.data;
-			bones = new ExposedList<Bone>(constraint.Bones.Count);
-			bones.AddRange(constraint.Bones);
-			target = constraint.target;
+		public TransformConstraint (TransformConstraint constraint, Skeleton skeleton)
+			: this(constraint.data, skeleton) {
+
 			mixRotate = constraint.mixRotate;
 			mixX = constraint.mixX;
 			mixY = constraint.mixY;
diff --git a/spine-csharp/src/package.json b/spine-csharp/src/package.json
index c24efb7bb..e581b197d 100644
--- a/spine-csharp/src/package.json
+++ b/spine-csharp/src/package.json
@@ -2,7 +2,7 @@
 	"name": "com.esotericsoftware.spine.spine-csharp",
 	"displayName": "spine-csharp Runtime",
 	"description": "This plugin provides the spine-csharp core runtime.",
-	"version": "4.2.20",
+	"version": "4.2.21",
 	"unity": "2018.3",
 	"author": {
 		"name": "Esoteric Software",