--- a/pmc/rectangle.cc
+++ b/pmc/rectangle.cc
@@ -18,7 +18,7 @@
     surface = s;
 }
 
-Rectangle::Rectangle (Surface * s, Vector p1, Vector p2, Vector p3, Vector p4)
+Rectangle::Rectangle (Surface * s, Vector& p1, Vector& p2, Vector& p3, Vector& p4)
 {
     P[0] = new Vector (p1);
     P[1] = new Vector (p2);