diff --git a/src/main/java/pythagoras/d/AffineTransform.java b/src/main/java/pythagoras/d/AffineTransform.java
index e6154b2..4186150 100644
--- a/src/main/java/pythagoras/d/AffineTransform.java
+++ b/src/main/java/pythagoras/d/AffineTransform.java
@@ -362,7 +362,7 @@ public class AffineTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public AffineTransform copy () {
         return new AffineTransform(m00, m01, m10, m11, tx, ty);
     }
 
diff --git a/src/main/java/pythagoras/d/IdentityTransform.java b/src/main/java/pythagoras/d/IdentityTransform.java
index 2cf3da3..17fb244 100644
--- a/src/main/java/pythagoras/d/IdentityTransform.java
+++ b/src/main/java/pythagoras/d/IdentityTransform.java
@@ -109,7 +109,7 @@ public class IdentityTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public IdentityTransform copy () {
         return this;
     }
 
diff --git a/src/main/java/pythagoras/f/AffineTransform.java b/src/main/java/pythagoras/f/AffineTransform.java
index c470239..c138425 100644
--- a/src/main/java/pythagoras/f/AffineTransform.java
+++ b/src/main/java/pythagoras/f/AffineTransform.java
@@ -362,7 +362,7 @@ public class AffineTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public AffineTransform copy () {
         return new AffineTransform(m00, m01, m10, m11, tx, ty);
     }
 
diff --git a/src/main/java/pythagoras/f/IdentityTransform.java b/src/main/java/pythagoras/f/IdentityTransform.java
index 6393c86..2e5a1a1 100644
--- a/src/main/java/pythagoras/f/IdentityTransform.java
+++ b/src/main/java/pythagoras/f/IdentityTransform.java
@@ -109,7 +109,7 @@ public class IdentityTransform extends AbstractTransform
     }
 
     @Override // from Transform
-    public Transform copy () {
+    public IdentityTransform copy () {
         return this;
     }