diff --git a/owlps-positioning/src/measurement.hh b/owlps-positioning/src/measurement.hh
index a578aaa..3b28d5b 100644
--- a/owlps-positioning/src/measurement.hh
+++ b/owlps-positioning/src/measurement.hh
@@ -152,7 +152,7 @@ inline Measurement::operator bool() const
 {
   return
     ap != NULL ||
-    ss_list.size() > 0 ;
+    ! ss_list.empty() ;
 }