diff --git a/TDS_3/include/CGAL/Triangulation_simplex_3.h b/TDS_3/include/CGAL/Triangulation_simplex_3.h
index 91db819c098..d00422df1ba 100644
--- a/TDS_3/include/CGAL/Triangulation_simplex_3.h
+++ b/TDS_3/include/CGAL/Triangulation_simplex_3.h
@@ -19,6 +19,7 @@
 
 #include <CGAL/assertions.h>
 #include <algorithm>
+#include <CGAL/IO/io.h>
 
 namespace CGAL {