diff --git a/include/boost/graph/erdos_renyi_generator.hpp b/include/boost/graph/erdos_renyi_generator.hpp
index 91c9b5e9..ce5e62a6 100644
--- a/include/boost/graph/erdos_renyi_generator.hpp
+++ b/include/boost/graph/erdos_renyi_generator.hpp
@@ -165,6 +165,7 @@ namespace boost {
     void next()
     {
       using std::sqrt;
+      using std::floor;
 
       // In order to get the edges from the generator in sorted order, one
       // effective (but slow) procedure would be to use a