diff --git a/Software/PC_Application/LibreVNA-GUI/Calibration/calibration.cpp b/Software/PC_Application/LibreVNA-GUI/Calibration/calibration.cpp
index c5c64a4..01aa638 100644
--- a/Software/PC_Application/LibreVNA-GUI/Calibration/calibration.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Calibration/calibration.cpp
@@ -603,6 +603,11 @@ void Calibration::edit()
         std::set<CalibrationMeasurement::Base*> m;
         auto selected = ui->table->selectionModel()->selectedRows();
         for(auto s : selected) {
+            auto meas = measurements[s.row()];
+            if(!meas->readyForMeasurement()) {
+                InformationBox::ShowError("Unable to measure", CalibrationMeasurement::Base::TypeToString(meas->getType())+" measurement is not ready, please check that a valid calibration standard is selected");
+                return;
+            }
             m.insert(measurements[s.row()]);
         }
         if(!CalibrationMeasurement::Base::canMeasureSimultaneously(m)) {
@@ -1659,7 +1664,7 @@ bool Calibration::canCompute(Calibration::CalType type, double *startFreq, doubl
                 // missing measurement
                 return false;
             } else if (!meas->readyForCalculation()){
-                // measurement not ready (either not calkit standard definded or no measurements
+                // measurement not ready (either not calkit standard definded or no measurements)
                 return false;
             } else {
                 foundMeasurements.push_back(meas);
diff --git a/Software/PC_Application/LibreVNA-GUI/Calibration/calibrationmeasurement.h b/Software/PC_Application/LibreVNA-GUI/Calibration/calibrationmeasurement.h
index e6b58f2..7050bf4 100644
--- a/Software/PC_Application/LibreVNA-GUI/Calibration/calibrationmeasurement.h
+++ b/Software/PC_Application/LibreVNA-GUI/Calibration/calibrationmeasurement.h
@@ -38,6 +38,7 @@ public:
     virtual double minFreq() = 0;
     virtual double maxFreq() = 0;
     virtual unsigned int numPoints() = 0;
+    virtual bool readyForMeasurement() {return false;}
     virtual bool readyForCalculation() {return false;}
 
     static std::vector<Type> availableTypes();
@@ -80,6 +81,7 @@ public:
     virtual double minFreq() override;
     virtual double maxFreq() override;
     virtual unsigned int numPoints() override {return points.size();}
+    virtual bool readyForMeasurement() override {return standard != nullptr;}
     virtual bool readyForCalculation() override {return standard && points.size() > 0;}
 
     virtual void clearPoints() override;
@@ -194,6 +196,7 @@ public:
     virtual double minFreq() override;
     virtual double maxFreq() override;
     virtual unsigned int numPoints() override {return points.size();}
+    virtual bool readyForMeasurement() override {return standard != nullptr;}
     virtual bool readyForCalculation() override {return standard && points.size() > 0;}
 
     virtual void clearPoints() override;
@@ -265,6 +268,7 @@ public:
     virtual double minFreq() override;
     virtual double maxFreq() override;
     virtual unsigned int numPoints() override;
+    virtual bool readyForMeasurement() override {return true;}
     virtual bool readyForCalculation() override {return points.size() > 0;}
 
     virtual void clearPoints() override;
diff --git a/Software/PC_Application/LibreVNA-GUI/Calibration/calstandard.cpp b/Software/PC_Application/LibreVNA-GUI/Calibration/calstandard.cpp
index 0c84a11..ea0f26c 100644
--- a/Software/PC_Application/LibreVNA-GUI/Calibration/calstandard.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Calibration/calstandard.cpp
@@ -120,7 +120,7 @@ void OnePort::clearMeasurement()
     delete touchstone;
     touchstone = nullptr;
     minFreq = std::numeric_limits<double>::lowest();
-    minFreq = std::numeric_limits<double>::max();
+    maxFreq = std::numeric_limits<double>::max();
 }
 
 nlohmann::json OnePort::toJSON()
@@ -538,7 +538,7 @@ void TwoPort::clearMeasurement()
     delete touchstone;
     touchstone = nullptr;
     minFreq = std::numeric_limits<double>::lowest();
-    minFreq = std::numeric_limits<double>::max();
+    maxFreq = std::numeric_limits<double>::max();
 }
 
 nlohmann::json TwoPort::toJSON()