diff --git a/pmc/rectangle.cc b/pmc/rectangle.cc
--- a/pmc/rectangle.cc
+++ b/pmc/rectangle.cc
@@ -3,7 +3,7 @@
  * Copyright (C) 2008 Markus Broeker
  */
 
-#include <rectangle.h>
+#include <rectangle.hpp>
 #include <cstdio>
 
 using namespace algebra;