diff --git a/src/Classic/AbsBeamline/Probe.h b/src/Classic/AbsBeamline/Probe.h
index 8fd6eedf26d0fa6dec435a943d10961a97477c93..04f04b63b84aef9d74ad225d7373ab1117c72a3f 100644
--- a/src/Classic/AbsBeamline/Probe.h
+++ b/src/Classic/AbsBeamline/Probe.h
@@ -93,7 +93,7 @@ private:
     ///@}
     double width_m;   ///< bin width, not used
     Point  geom_m[5]; ///< actual geometry positions with adaptive width such that each particle hits probe once per turn
-    int step_m; ///< Step size of the probe (bin width in histogram file)
+    double step_m; ///< Step size of the probe (bin width in histogram file)
 
     double A_m, B_m,R_m, C_m;
     void setGeom(const double dist);