diff --git a/libtorrent/include/libtorrent/ptime.hpp b/libtorrent/include/libtorrent/ptime.hpp
index 7b8b9c13..bf4016d3 100644
--- a/libtorrent/include/libtorrent/ptime.hpp
+++ b/libtorrent/include/libtorrent/ptime.hpp
@@ -72,7 +72,8 @@ namespace libtorrent
 		{ return time_duration(diff + c.diff); }
 		time_duration operator-(time_duration const& c)
 		{ return time_duration(diff - c.diff); }
-		time_duration operator*(double rhs) const { return time_duration( boost::int64_t (diff * rhs) ); }
+		time_duration operator*(const double rhs) const
+		{ return time_duration( boost::int64_t (diff * rhs) ); }
 
 		// internal
 		boost::int64_t diff;