diff --git a/Software/PC_Application/LibreVNA-GUI/Traces/trace.cpp b/Software/PC_Application/LibreVNA-GUI/Traces/trace.cpp
index 7f82690..ee017db 100644
--- a/Software/PC_Application/LibreVNA-GUI/Traces/trace.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Traces/trace.cpp
@@ -408,10 +408,10 @@ void Trace::setMathFormula(const QString &newMathFormula)
     scheduleMathCalculation(0, data.size());
 }
 
-bool Trace::mathFormularValid() const
+QString Trace::getMathFormulaError() const
 {
     if(mathFormula.isEmpty()) {
-        return false;
+        return "Math formula must not be empty";
     }
     try {
         ParserX parser(pckCOMMON | pckUNIT | pckCOMPLEX);
@@ -428,15 +428,15 @@ bool Trace::mathFormularValid() const
                 }
             }
             if(!found) {
-                return false;
+                return "Unknown variable: "+varName;
             }
         }
     } catch (const ParserError &e) {
         // parser error occurred
-        return false;
+        return "Parsing failed: " + QString::fromStdString(e.GetMsg());
     }
     // all variables used in the expression are set as math sources
-    return true;
+    return "";
 }
 
 bool Trace::resolveMathSourceHashes()
diff --git a/Software/PC_Application/LibreVNA-GUI/Traces/trace.h b/Software/PC_Application/LibreVNA-GUI/Traces/trace.h
index d4b813a..2e4a500 100644
--- a/Software/PC_Application/LibreVNA-GUI/Traces/trace.h
+++ b/Software/PC_Application/LibreVNA-GUI/Traces/trace.h
@@ -166,7 +166,7 @@ public:
 
     const QString &getMathFormula() const;
     void setMathFormula(const QString &newMathFormula);
-    bool mathFormularValid() const;
+    QString getMathFormulaError() const;
 
     // When loading setups, some traces may be used as a math source before they are loaded.
     // If that happens, their hashes are added to a list. Call this function for every new trace
diff --git a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.cpp b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.cpp
index fab0edb..02195a7 100644
--- a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.cpp
@@ -56,7 +56,7 @@ TraceEditDialog::TraceEditDialog(Trace &t, QWidget *parent) :
     connect(ui->bMath, &QPushButton::clicked, [&](bool math){
        if(math) {
            ui->stack->setCurrentIndex(3);
-           ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(t.mathFormularValid());
+           ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(updateMathFormulaStatus());
            ui->impedance->setEnabled(true);
        }
     });
@@ -146,10 +146,11 @@ TraceEditDialog::TraceEditDialog(Trace &t, QWidget *parent) :
     connect(ui->csvImport, &CSVImport::filenameChanged, updateCSVFileStatus);
 
     // Math source configuration
+    ui->lMathFormula->setText(t.getMathFormula());
     if(t.getModel()) {
         connect(ui->lMathFormula, &QLineEdit::textChanged, [&](){
             t.setMathFormula(ui->lMathFormula->text());
-            ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(t.mathFormularValid());
+            ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(updateMathFormulaStatus());
         });
 
         ui->mathTraceTable->setColumnCount(2);
@@ -212,7 +213,7 @@ TraceEditDialog::TraceEditDialog(Trace &t, QWidget *parent) :
                 t.addMathSource(trace, item->text());
             }
             ui->mathTraceTable->blockSignals(false);
-            ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(t.mathFormularValid());
+            ui->buttonBox->button(QDialogButtonBox::Ok)->setEnabled(updateMathFormulaStatus());
         });
     }
 
@@ -381,6 +382,21 @@ void TraceEditDialog::okClicked()
     delete this;
 }
 
+bool TraceEditDialog::updateMathFormulaStatus()
+{
+    auto error = trace.getMathFormulaError();
+    if(error.isEmpty()) {
+        // all good
+        ui->lMathFormulaStatus->setText("Math formula valid");
+        ui->lMathFormulaStatus->setStyleSheet("");
+        return true;
+    } else {
+        ui->lMathFormulaStatus->setText(error);
+        ui->lMathFormulaStatus->setStyleSheet("QLabel { color : red; }");
+        return false;
+    }
+}
+
 MathModel::MathModel(Trace &t, QObject *parent)
     : QAbstractTableModel(parent),
       t(t)
diff --git a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.h b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.h
index e8b31b1..f00d237 100644
--- a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.h
+++ b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.h
@@ -49,6 +49,7 @@ private slots:
     void okClicked();
 
 private:
+    bool updateMathFormulaStatus();
     Ui::TraceEditDialog *ui;
     Trace &trace;
     bool VNAtrace;
diff --git a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.ui b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.ui
index da30276..ea98621 100644
--- a/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.ui
+++ b/Software/PC_Application/LibreVNA-GUI/Traces/traceeditdialog.ui
@@ -143,7 +143,7 @@
        <item>
         <widget class="QStackedWidget" name="stack">
          <property name="currentIndex">
-          <number>0</number>
+          <number>3</number>
          </property>
          <widget class="QWidget" name="LivePage">
           <layout class="QFormLayout" name="formLayout_2">
@@ -239,6 +239,16 @@
              </item>
             </layout>
            </item>
+           <item>
+            <widget class="QLabel" name="lMathFormulaStatus">
+             <property name="text">
+              <string/>
+             </property>
+             <property name="wordWrap">
+              <bool>true</bool>
+             </property>
+            </widget>
+           </item>
           </layout>
          </widget>
         </widget>