diff --git a/owlps-positioning/src/timestamp.hh b/owlps-positioning/src/timestamp.hh
index d1a8e5b..de2ae8e 100644
--- a/owlps-positioning/src/timestamp.hh
+++ b/owlps-positioning/src/timestamp.hh
@@ -228,7 +228,7 @@ inline bool Timestamp::operator>=(const uint64_t source) const
 
 inline Timestamp::operator bool() const
 {
-  return static_cast<uint64_t>(*this) > 0 ;
+  return timestamp.tv_sec > 0 || timestamp.tv_nsec > 0 ;
 }