diff --git a/owlps-positioning/src/point3d.cc b/owlps-positioning/src/point3d.cc
index e496f00..00d3606 100644
--- a/owlps-positioning/src/point3d.cc
+++ b/owlps-positioning/src/point3d.cc
@@ -109,7 +109,7 @@ bool Point3D::operator<(const Point3D &source) const
 }
 
 
-Point3D::operator string(void) const
+Point3D::operator std::string(void) const
 {
   ostringstream oss ;
   oss << *this ;