diff --git a/src/file.cpp b/src/file.cpp
index 7bf21ef11..ef6432f75 100644
--- a/src/file.cpp
+++ b/src/file.cpp
@@ -453,8 +453,9 @@ namespace libtorrent
 		std::string ret;
 		int target_size = lhs.size() + rhs.size() + 2;
 		ret.resize(target_size);
-		snprintf(&ret[0], target_size, "%s%s%s", lhs.c_str()
+		target_size = snprintf(&ret[0], target_size, "%s%s%s", lhs.c_str()
 			, (need_sep?TORRENT_SEPARATOR:""), rhs.c_str());
+		ret.resize(target_size);
 		return ret;
 	}