diff --git a/NPSimulation/src/DetectorConstruction.cc b/NPSimulation/src/DetectorConstruction.cc
index a09b3a79a8d1aa753634ca3f6ec0af70961bb97b..40f19eadb7511b1c660fe7e035f46dc7bad007da 100644
--- a/NPSimulation/src/DetectorConstruction.cc
+++ b/NPSimulation/src/DetectorConstruction.cc
@@ -288,7 +288,7 @@ void DetectorConstruction::ReadAllSensitive(const G4Event* event)
    if(m_Detectors.size()>0)
    m_Detectors[0]->GetInterCoordPointer()->Clear();
 
-   for (ushort i = 0 ; i < m_Detectors.size() ; i++) {
+   for (unsigned short i = 0 ; i < m_Detectors.size() ; i++) {
       m_Detectors[i]->ReadSensitive(event);
    }
 }