diff --git a/tools/lammps-gui/chartviewer.cpp b/tools/lammps-gui/chartviewer.cpp
index 71ba07de4c..4ea5449f3f 100644
--- a/tools/lammps-gui/chartviewer.cpp
+++ b/tools/lammps-gui/chartviewer.cpp
@@ -424,7 +424,7 @@ void ChartViewer::add_data(int step, double data)
     if (last_step < step) {
         last_step = step;
 
-        // do not add data that deviates by more than 5 sigma from the average
+        // do not add data that deviates by more than 4 sigma from the average
         // over the last 5 to 20 data items.  this is a hack to work around
         // getting corrupted data from lammps_get_last_thermo()
         const auto &points = series->points();
@@ -442,7 +442,7 @@ void ChartViewer::add_data(int step, double data)
             const double num   = count - first;
             const double avg   = ysum / num;
             const double avgsq = ysumsq / num;
-            if (fabs(data - avg) > (5.0 * sqrt(avgsq - (avg * avg)))) return;
+            if (fabs(data - avg) > (4.0 * sqrt(avgsq - (avg * avg)))) return;
         }
         series->append(step, data);