diff --git a/tools/lammps-gui/chartviewer.cpp b/tools/lammps-gui/chartviewer.cpp
index 4779bf758b..413a169468 100644
--- a/tools/lammps-gui/chartviewer.cpp
+++ b/tools/lammps-gui/chartviewer.cpp
@@ -345,15 +345,34 @@ ChartViewer::ChartViewer(const QString &title, int _index, QWidget *parent) :
 
 void ChartViewer::add_data(int step, double data)
 {
-    QSettings settings;
-    auto updchart = settings.value("updchart", "500").toInt();
-
     if (last_step < step) {
         last_step = step;
 
+        // do not add data that deviates by more than 5 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();
+        const auto count   = points.count();
+        if (count > 4) {
+            double ysum   = 0.0;
+            double ysumsq = 0.0;
+            int first     = count - 20;
+            if (first < 0) first = 0;
+            for (int i = first; i < count; ++i) {
+                double val = points[i].y();
+                ysum += val;
+                ysumsq += val * val;
+            }
+            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;
+        }
         series->append(step, data);
 
-        if (last_update.msecsTo(QTime::currentTime()) > updchart) {
+        QSettings settings;
+        // update the chart display only after at least updchart milliseconds have passed
+        if (last_update.msecsTo(QTime::currentTime()) > settings.value("updchart", "500").toInt()) {
             last_update = QTime::currentTime();
             reset_zoom();
         }