diff --git a/src/main/java/pythagoras/d/Vector.java b/src/main/java/pythagoras/d/Vector.java
index 1dad4e7..7e35290 100644
--- a/src/main/java/pythagoras/d/Vector.java
+++ b/src/main/java/pythagoras/d/Vector.java
@@ -105,7 +105,7 @@ public class Vector extends AbstractVector
 
     /** Copies the elements of another vector.
      * @return a reference to this vector, for chaining. */
-    public Vector set (IVector other) {
+    public Vector set (XY other) {
         return set(other.x(), other.y());
     }
 
diff --git a/src/main/java/pythagoras/f/Vector.java b/src/main/java/pythagoras/f/Vector.java
index 62faecd..698b80c 100644
--- a/src/main/java/pythagoras/f/Vector.java
+++ b/src/main/java/pythagoras/f/Vector.java
@@ -105,7 +105,7 @@ public class Vector extends AbstractVector
 
     /** Copies the elements of another vector.
      * @return a reference to this vector, for chaining. */
-    public Vector set (IVector other) {
+    public Vector set (XY other) {
         return set(other.x(), other.y());
     }