diff --git a/build.jam b/build.jam
index 0cf6dc092..bdb213571 100644
--- a/build.jam
+++ b/build.jam
@@ -3,6 +3,8 @@
 # (See accompanying file LICENSE_1_0.txt or copy at
 # http://www.boost.org/LICENSE_1_0.txt)
 
+require-b2 5.1 ;
+
 import project ;
 
 project /boost/ublas