diff --git a/include/exiv2/types.hpp b/include/exiv2/types.hpp
index 73280c09..2113f7c3 100644
--- a/include/exiv2/types.hpp
+++ b/include/exiv2/types.hpp
@@ -546,7 +546,7 @@ namespace Exiv2 {
     {
         std::istringstream is(s);
         T tmp;
-        ok = is >> tmp ? true : false;
+        ok = (is >> tmp) ? true : false;
         std::string rest;
         is >> std::skipws >> rest;
         if (!rest.empty()) ok = false;