diff --git a/src/musredit_qt6/mupp/PmuppGui.cpp b/src/musredit_qt6/mupp/PmuppGui.cpp
index c1965a337..c911d6898 100644
--- a/src/musredit_qt6/mupp/PmuppGui.cpp
+++ b/src/musredit_qt6/mupp/PmuppGui.cpp
@@ -1955,8 +1955,9 @@ void PmuppGui::createMacro()
   fout << "  gStyle->SetCanvasColor(TColor::GetColor(255,255,255)); // canvas bkg to white" << Qt::endl;
   fout << Qt::endl;
   fout << "  Int_t nn=0, i=0;" << Qt::endl;
-  fout << "  Double_t null[512];" << Qt::endl;
   fout << "  Double_t xx[512];" << Qt::endl;
+  fout << "  Double_t xxPosErr[512];" << Qt::endl;
+  fout << "  Double_t xxNegErr[512];" << Qt::endl;
   fout << "  Double_t yy[512];" << Qt::endl;
   fout << "  Double_t yyPosErr[512];" << Qt::endl;
   fout << "  Double_t yyNegErr[512];" << Qt::endl;
@@ -1966,7 +1967,7 @@ void PmuppGui::createMacro()
   QString collName("");
   QString xLabel(""), yLabel("");
   char gLabel[128];
-  QVector<double> xx, yy, yyPosErr, yyNegErr;
+  QVector<double> xx, xxPosErr, xxNegErr, yy, yyPosErr, yyNegErr;
   double xMin=1.0e10, xMax=-1.0e10, yMin=1.0e10, yMax=-1.0e10;
   bool ok;
   for (int i=0; i<fXY.size(); i++) {
@@ -1976,13 +1977,19 @@ void PmuppGui::createMacro()
     xLabel = fXY[i].getXlabel();
     pos = xLabel.indexOf(" (-");
     xLabel.remove(pos, xLabel.length()-pos);
-    // get x-vector
+    // get x-vector and x-errors (x-errors are optional; use 0.0 if not available)
     xx = getValues(collName, xLabel, ok);
     if (!ok) {
       QString msg = QString("Couldn't get x-axis data from '%1', coll: '%2'").arg(xLabel).arg(collName);
       QMessageBox::critical(this, "ERROR", msg);
       return;
     }
+    xxPosErr = getPosErr(collName, xLabel, ok);
+    if (!ok)
+      xxPosErr = QVector<double>(xx.size(), 0.0);
+    xxNegErr = getNegErr(collName, xLabel, ok);
+    if (!ok)
+      xxNegErr = QVector<double>(xx.size(), 0.0);
     getMinMax(xx, xMin, xMax);
     // a couple of x-vector specifics
     if ((xLabel == "dataT") || (xLabel == "dataE"))
@@ -2019,14 +2026,18 @@ void PmuppGui::createMacro()
       snprintf(gLabel, sizeof(gLabel), "g_%d_%d", i, j);
       fout << "  nn = " << xx.size() << ";" << Qt::endl;
       fout << Qt::endl;
-      fout << "  // null value vector" << Qt::endl;
-      for (int k=0; k<xx.size(); k++) {
-        fout << "  null[" << k << "]=0.0;" << Qt::endl;
-      }
       fout << "  // xx" << Qt::endl;
       for (int k=0; k<xx.size(); k++) {
         fout << "  xx[" << k << "]=" << xx[k] << ";" << Qt::endl;
       }
+      fout << "  // xxPosErr" << Qt::endl;
+      for (int k=0; k<xx.size(); k++) {
+        fout << "  xxPosErr[" << k << "]=" << xxPosErr[k] << ";" << Qt::endl;
+      }
+      fout << "  // xxNegErr" << Qt::endl;
+      for (int k=0; k<xx.size(); k++) {
+        fout << "  xxNegErr[" << k << "]=" << fabs(xxNegErr[k]) << ";" << Qt::endl;
+      }
       fout << "  // yy" << Qt::endl;
       for (int k=0; k<xx.size(); k++) {
         fout << "  yy[" << k << "]=" << yy[k] << ";" << Qt::endl;
@@ -2040,7 +2051,7 @@ void PmuppGui::createMacro()
         fout << "  yyNegErr[" << k << "]=" << fabs(yyNegErr[k]) << ";" << Qt::endl;
       }
       fout << Qt::endl;
-      fout << "  TGraphAsymmErrors *" << gLabel << " = new TGraphAsymmErrors(nn, xx, yy, null, null, yyNegErr, yyPosErr);" << Qt::endl;
+      fout << "  TGraphAsymmErrors *" << gLabel << " = new TGraphAsymmErrors(nn, xx, yy, xxNegErr, xxPosErr, yyNegErr, yyPosErr);" << Qt::endl;
     }
   }
   fout << Qt::endl;
@@ -2138,7 +2149,7 @@ void PmuppGui::plot()
   int collTag = -1, pos;
   QString collName("");
   QString xLabel(""), yLabel("");
-  QVector<double> xx, yy, yyPosErr, yyNegErr;
+  QVector<double> xx, xxPosErr, xxNegErr, yy, yyPosErr, yyNegErr;
   QVector< QVector<double> > yyy, yyyPosErr, yyyNegErr;
   bool ok;
 
@@ -2165,13 +2176,19 @@ void PmuppGui::plot()
     xLabel = fXY[i].getXlabel();
     pos = xLabel.indexOf(" (-");
     xLabel.remove(pos, xLabel.length()-pos);
-    // get x-vector
+    // get x-vector and x-errors (x-errors are optional; use 0.0 if not available)
     xx = getValues(collName, xLabel, ok);
     if (!ok) {
       QString msg = QString("Couldn't get x-axis data from '%1', coll: '%2'").arg(xLabel).arg(collName);
       QMessageBox::critical(this, "ERROR", msg);
       return;
     }
+    xxPosErr = getPosErr(collName, xLabel, ok);
+    if (!ok)
+      xxPosErr = QVector<double>(xx.size(), 0.0);
+    xxNegErr = getNegErr(collName, xLabel, ok);
+    if (!ok)
+      xxNegErr = QVector<double>(xx.size(), 0.0);
 
     xLabel = substituteDefaultLabels(xLabel);
     fout << "xLabel: " << xLabel << ", ";
@@ -2253,9 +2270,9 @@ void PmuppGui::plot()
       }
     }
 
-    // data
+    // data: x, xPosErr, xNegErr, y1, y1PosErr, y1NegErr, ...
     for (int j=0; j<xx.size(); j++) {
-      fout << xx[j] << ", ";
+      fout << xx[j] << ", " << xxPosErr[j] << ", " << xxNegErr[j] << ", ";
       for (int k=0; k<yyy.size()-1; k++) {
         fout << yyy[k][j] << ", " << yyyPosErr[k][j] << ", " << yyyNegErr[k][j] << ", ";
       }
diff --git a/src/musredit_qt6/mupp/PmuppScript.cpp b/src/musredit_qt6/mupp/PmuppScript.cpp
index d23c0bbef..29b2709ac 100644
--- a/src/musredit_qt6/mupp/PmuppScript.cpp
+++ b/src/musredit_qt6/mupp/PmuppScript.cpp
@@ -784,15 +784,16 @@ int PmuppScript::macro(const QString str, const QString plotFln)
   fout << "  gStyle->SetCanvasColor(TColor::GetColor(255,255,255)); // canvas bkg to white" << Qt::endl;
   fout << Qt::endl;
   fout << "  Int_t nn=0, i=0;" << Qt::endl;
-  fout << "  Double_t null[512];" << Qt::endl;
   fout << "  Double_t xx[512];" << Qt::endl;
+  fout << "  Double_t xxPosErr[512];" << Qt::endl;
+  fout << "  Double_t xxNegErr[512];" << Qt::endl;
   fout << "  Double_t yy[512];" << Qt::endl;
   fout << "  Double_t yyPosErr[512];" << Qt::endl;
   fout << "  Double_t yyNegErr[512];" << Qt::endl;
   fout << Qt::endl;
 
   // write data
-  QVector<double> xx, yy, yyPosErr, yyNegErr;
+  QVector<double> xx, xxPosErr, xxNegErr, yy, yyPosErr, yyNegErr;
   QString collName;
   int count=0;
   double x_min=0.0, x_max=0.0, x_min_new=0.0, x_max_new=0.0, y_min=0.0, y_max=0.0, y_min_new=0.0, y_max_new=0.0;
@@ -812,6 +813,19 @@ int PmuppScript::macro(const QString str, const QString plotFln)
       std::vector<double> xVal = fVarHandler[idx].getValues();
       QVector<double> qvec(xVal.begin(), xVal.end());
       xx = qvec;
+      // use variable errors for x
+      std::vector<double> xErr = fVarHandler[idx].getErrors();
+      QVector<double> qvecE(xErr.begin(), xErr.end());
+      xxPosErr = qvecE;
+      xxNegErr = qvecE;
+    } else {
+      // x-errors from parameter data handler (0.0 if not available)
+      xxPosErr = fParamDataHandler->GetPosErr(collName, fPlotInfo[i].xLabel);
+      if (xxPosErr.size() == 0)
+        xxPosErr = QVector<double>(xx.size(), 0.0);
+      xxNegErr = fParamDataHandler->GetNegErr(collName, fPlotInfo[i].xLabel);
+      if (xxNegErr.size() == 0)
+        xxNegErr = QVector<double>(xx.size(), 0.0);
     }
     // get x-axis min/max
     minMax(xx, x_min, x_max);
@@ -858,14 +872,18 @@ int PmuppScript::macro(const QString str, const QString plotFln)
       }
       fout << "  // " << ++count << ". data set" << Qt::endl;
       fout << "  nn = " << xx.size() << ";" << Qt::endl;
-      fout << "  // null-values" << Qt::endl;
-      for (int k=0; k<xx.size(); k++) {
-        fout << "  null[" << k << "]=0.0;" << Qt::endl;
-      }
       fout << "  // x-values" << Qt::endl;
       for (int k=0; k<xx.size(); k++) {
         fout << "  xx[" << k << "]=" << xx[k] << ";" << Qt::endl;
       }
+      fout << "  // xxPosErr-values" << Qt::endl;
+      for (int k=0; k<xxPosErr.size(); k++) {
+        fout << "  xxPosErr[" << k << "]=" << fabs(xxPosErr[k]) << ";" << Qt::endl;
+      }
+      fout << "  // xxNegErr-values" << Qt::endl;
+      for (int k=0; k<xxNegErr.size(); k++) {
+        fout << "  xxNegErr[" << k << "]=" << fabs(xxNegErr[k]) << ";" << Qt::endl;
+      }
       fout << "  // y-values" << Qt::endl;
       for (int k=0; k<yy.size(); k++) {
         dval = yy[k];
@@ -891,7 +909,7 @@ int PmuppScript::macro(const QString str, const QString plotFln)
         fout << "  yyPosErr[" << k << "]=" << dval << ";" << Qt::endl;
       }
       fout << Qt::endl;
-      fout << "  TGraphAsymmErrors *g_" << i << "_" << j << " = new TGraphAsymmErrors(nn, xx, yy, null, null, yyNegErr, yyPosErr);" << Qt::endl;
+      fout << "  TGraphAsymmErrors *g_" << i << "_" << j << " = new TGraphAsymmErrors(nn, xx, yy, xxNegErr, xxPosErr, yyNegErr, yyPosErr);" << Qt::endl;
       fout << Qt::endl;
     }
   }
diff --git a/src/musredit_qt6/mupp/plotter/PMuppCanvas.cpp b/src/musredit_qt6/mupp/plotter/PMuppCanvas.cpp
index 7a7b6e5fa..16aff5573 100644
--- a/src/musredit_qt6/mupp/plotter/PMuppCanvas.cpp
+++ b/src/musredit_qt6/mupp/plotter/PMuppCanvas.cpp
@@ -26,7 +26,7 @@
   - Tab-separated values
   - First line: "PLOT_DATA" header
   - Collection blocks with name, x-label, y-labels, and data points
-  - Each data point: x-value, y-value, positive error, negative error
+  - Each data point: x-value, x-pos-error, x-neg-error, y-value, y-pos-error, y-neg-error, ...
 
 ***************************************************************************/
 
@@ -421,7 +421,7 @@ int PMuppCanvas::ReadPlotData(const Char_t *fln)
         fin.close();
         return -4;
       }
-      if (tok->GetEntries() != (noOfDataTokens-1)*3+1) {
+      if (tok->GetEntries() != noOfDataTokens*3) {
         std::cerr << "**ERROR** number of token in data line (" << tok->GetEntries() << ") is inconsistent with no of labels (" << noOfDataTokens << ")." << std::endl;
         fin.close();
         return -4;
@@ -431,7 +431,7 @@ int PMuppCanvas::ReadPlotData(const Char_t *fln)
       data.yValue.resize(noOfDataTokens-1);
 
       // raw data point
-      // x-value
+      // x-value (token 0)
       ostr = dynamic_cast<TObjString*>(tok->At(0));
       str = ostr->GetString();
       if (!str.IsFloat()) {
@@ -441,9 +441,29 @@ int PMuppCanvas::ReadPlotData(const Char_t *fln)
       }
       data.xValue.push_back(str.Atof());
 
-      // y-value(s)
+      // pos x error-value (token 1)
+      ostr = dynamic_cast<TObjString*>(tok->At(1));
+      str = ostr->GetString();
+      if (!str.IsFloat()) {
+        std::cerr << "**ERROR** token found in data line is not a number (" << str << ")." << std::endl;
+        fin.close();
+        return -5;
+      }
+      data.xErrPos.push_back(str.Atof());
+
+      // neg x error-value (token 2)
+      ostr = dynamic_cast<TObjString*>(tok->At(2));
+      str = ostr->GetString();
+      if (!str.IsFloat()) {
+        std::cerr << "**ERROR** token found in data line is not a number (" << str << ")." << std::endl;
+        fin.close();
+        return -5;
+      }
+      data.xErrNeg.push_back(str.Atof());
+
+      // y-value(s): starting at token 3, each group of 3 = y, yposErr, ynegErr
       Int_t idx=0;
-      for (Int_t i=1; i<tok->GetEntries(); i+=3) {
+      for (Int_t i=3; i<tok->GetEntries(); i+=3) {
         // y-value
         ostr = dynamic_cast<TObjString*>(tok->At(i));
         str = ostr->GetString();
@@ -525,6 +545,8 @@ void PMuppCanvas::InitDataCollection(PDataCollection &coll)
   coll.xLabel = TString("");
   coll.yLabel.clear();
   coll.xValue.clear();
+  coll.xErrPos.clear();
+  coll.xErrNeg.clear();
   coll.yValue.clear();
 }
 
@@ -553,7 +575,8 @@ void PMuppCanvas::UpdateGraphs()
         gg = new TGraphAsymmErrors(fPlotData[i].xValue.size());
         for (UInt_t k=0; k<fPlotData[i].yValue[j].size(); k++) {
           gg->SetPoint(k, fPlotData[i].xValue[k], fPlotData[i].yValue[j][k].y);
-          gg->SetPointError(k, 0.0, 0.0, fabs(fPlotData[i].yValue[j][k].eYneg), fPlotData[i].yValue[j][k].eYpos);
+          gg->SetPointError(k, fabs(fPlotData[i].xErrNeg[k]), fPlotData[i].xErrPos[k],
+                            fabs(fPlotData[i].yValue[j][k].eYneg), fPlotData[i].yValue[j][k].eYpos);
           // set marker style and size
           if (idxS < fMarkerStyleList.size()) {
             gg->SetMarkerStyle(fMarkerStyleList[idxS]);
@@ -666,12 +689,14 @@ void PMuppCanvas::ExportData()
     std::ofstream fout(fi.fFilename, std::ios_base::out);
     // write header
     for (int i=0; i<fPlotData.size(); i++) {
-      fout << fPlotData[i].xLabel.Strip(TString::kLeading).Data() << ", ";
+      TString xl = fPlotData[i].xLabel.Strip(TString::kLeading);
+      fout << xl.Data() << ", " << xl.Data() << "ErrPos, " << xl.Data() << "ErrNeg, ";
       for (int j=0; j<fPlotData[i].yLabel.size(); j++) {
-        if ((i == fPlotData.size()-1) && (j == fPlotData[i].yLabel.size()-1))
-          fout << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << ", " << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << "ErrPos, " << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << "ErrNeg";
+        TString yl = fPlotData[i].yLabel[j].Strip(TString::kLeading);
+        if ((i == (int)fPlotData.size()-1) && (j == (int)fPlotData[i].yLabel.size()-1))
+          fout << yl.Data() << ", " << yl.Data() << "ErrPos, " << yl.Data() << "ErrNeg";
         else
-          fout << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << ", " << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << "ErrPos, " << fPlotData[i].yLabel[j].Strip(TString::kLeading).Data() << "ErrNeg, ";
+          fout << yl.Data() << ", " << yl.Data() << "ErrPos, " << yl.Data() << "ErrNeg, ";
       }
     }
     fout << std::endl;
@@ -679,21 +704,21 @@ void PMuppCanvas::ExportData()
     // search the longest data set
     Int_t maxLength=0;
     for (int i=0; i<fPlotData.size(); i++) {
-      if (maxLength < fPlotData[i].xValue.size())
+      if (maxLength < (Int_t)fPlotData[i].xValue.size())
         maxLength = fPlotData[i].xValue.size();
     }
     // write data
     for (int i=0; i<maxLength; i++) { // maximal data set length
       for (int j=0; j<fPlotData.size(); j++) { // number of x-data sets
-        // write x-value
-        if (i < fPlotData[j].xValue.size()) // make sure that the entry exists
-          fout << fPlotData[j].xValue[i] << ", ";
+        // write x-value and x-errors
+        if (i < (int)fPlotData[j].xValue.size())
+          fout << fPlotData[j].xValue[i] << ", " << fPlotData[j].xErrPos[i] << ", " << fPlotData[j].xErrNeg[i] << ", ";
         else
-          fout << " , ";
+          fout << " ,  ,  , ";
         // write y-value and y-value error
         for (int k=0; k<fPlotData[j].yValue.size(); k++) { // number of y-data sets
-          if ((j == fPlotData.size()-1) && (k == fPlotData[j].yValue.size()-1))
-            if (i < fPlotData[j].yValue[k].size())
+          if ((j == (int)fPlotData.size()-1) && (k == (int)fPlotData[j].yValue.size()-1))
+            if (i < (int)fPlotData[j].yValue[k].size())
               fout << fPlotData[j].yValue[k][i].y << ", " << fPlotData[j].yValue[k][i].eYpos << ", " << fPlotData[j].yValue[k][i].eYneg;
             else
               fout << ", , , ";
diff --git a/src/musredit_qt6/mupp/plotter/PMuppCanvas.h b/src/musredit_qt6/mupp/plotter/PMuppCanvas.h
index 447c26959..920b046ca 100644
--- a/src/musredit_qt6/mupp/plotter/PMuppCanvas.h
+++ b/src/musredit_qt6/mupp/plotter/PMuppCanvas.h
@@ -93,6 +93,8 @@ struct PDataCollection {
   TString xLabel;                                ///< label for the x-axis
   PStringVector yLabel;                          ///< labels for each y-dataset
   PDoubleVector xValue;                          ///< x-values (common to all y-datasets)
+  PDoubleVector xErrPos;                         ///< positive x-errors (upward)
+  PDoubleVector xErrNeg;                         ///< negative x-errors (downward)
   std::vector< std::vector<PDataPoint> > yValue; ///< y-values with errors for each dataset
 };