diff --git a/src/gui/editorwidgets/qgsvaluemapconfigdlg.cpp b/src/gui/editorwidgets/qgsvaluemapconfigdlg.cpp
index 879a38f7575a..5cae47fadafd 100644
--- a/src/gui/editorwidgets/qgsvaluemapconfigdlg.cpp
+++ b/src/gui/editorwidgets/qgsvaluemapconfigdlg.cpp
@@ -33,6 +33,9 @@ QgsValueMapConfigDlg::QgsValueMapConfigDlg( QgsVectorLayer *vl, int fieldIdx, QW
 {
   setupUi( this );
 
+  mValueMapErrorsLabel->setVisible( false );
+  mValueMapErrorsLabel->setStyleSheet( QStringLiteral( "QLabel { color : red; }" ) );
+
   tableWidget->insertRow( 0 );
 
   tableWidget->horizontalHeader()->setSectionsClickable( true );
@@ -90,12 +93,13 @@ void QgsValueMapConfigDlg::setConfig( const QVariantMap &config )
   }
 
   QList<QVariant> valueList = config.value( QStringLiteral( "map" ) ).toList();
+  QList<QPair<QString, QVariant>> orderedList;
 
   if ( valueList.count() > 0 )
   {
     for ( int i = 0, row = 0; i < valueList.count(); i++, row++ )
     {
-      setRow( row, valueList[i].toMap().constBegin().value().toString(), valueList[i].toMap().constBegin().key() );
+      orderedList.append( qMakePair( valueList[i].toMap().constBegin().value().toString(), valueList[i].toMap().constBegin().key() ) );
     }
   }
   else
@@ -105,11 +109,14 @@ void QgsValueMapConfigDlg::setConfig( const QVariantMap &config )
     for ( QVariantMap::ConstIterator mit = values.constBegin(); mit != values.constEnd(); mit++, row++ )
     {
       if ( QgsVariantUtils::isNull( mit.value() ) )
-        setRow( row, mit.key(), QString() );
+        orderedList.append( qMakePair( mit.key(), QVariant() ) );
       else
-        setRow( row, mit.value().toString(), mit.key() );
+        orderedList.append( qMakePair( mit.value().toString(), mit.key() ) );
     }
   }
+
+  updateMap( orderedList, false );
+
 }
 
 void QgsValueMapConfigDlg::vCellChanged( int row, int column )
@@ -120,6 +127,24 @@ void QgsValueMapConfigDlg::vCellChanged( int row, int column )
     tableWidget->insertRow( row + 1 );
   } //else check type
 
+  if ( layer()->fields().exists( field() ) )
+  {
+    // check cell value
+    QTableWidgetItem *item = tableWidget->item( row, 0 );
+    if ( item )
+    {
+      const QString validValue = checkValueLength( item->text() );
+      if ( validValue.length() != item->text().length() )
+      {
+        const QString errorMessage = tr( "Value '%1' has been trimmed (maximum field length: %2)" )
+                                     .arg( item->text(), QString::number( layer()->fields().field( field() ).length() ) );
+        item->setText( validValue );
+        mValueMapErrorsLabel->setVisible( true );
+        mValueMapErrorsLabel->setText( QStringLiteral( "%1<br>%2" ).arg( errorMessage, mValueMapErrorsLabel->text() ) );
+      }
+    }
+  }
+
   emit changed();
 }
 
@@ -163,6 +188,8 @@ void QgsValueMapConfigDlg::updateMap( const QMap<QString, QVariant> &map, bool i
 void QgsValueMapConfigDlg::updateMap( const QList<QPair<QString, QVariant>> &list, bool insertNull )
 {
   tableWidget->clearContents();
+  mValueMapErrorsLabel->setVisible( false );
+
   for ( int i = tableWidget->rowCount() - 1; i > 0; i-- )
   {
     tableWidget->removeRow( i );
@@ -175,16 +202,62 @@ void QgsValueMapConfigDlg::updateMap( const QList<QPair<QString, QVariant>> &lis
     ++row;
   }
 
+  constexpr int maxOverflowErrors { 5 };
+  QStringList reportedErrors;
+  const bool hasField { layer()->fields().exists( field() ) };
+  const QgsField mappedField { hasField ? layer()->fields().field( field() ) : QgsField() };
+
   for ( const auto &pair : list )
   {
     if ( QgsVariantUtils::isNull( pair.second ) )
       setRow( row, pair.first, QString() );
     else
-      setRow( row, pair.first, pair.second.toString() );
+    {
+      const QString value { pair.first };
+      // Check value
+      const QString validValue = checkValueLength( value ) ;
+
+      if ( validValue.length() != value.length() )
+      {
+
+        if ( reportedErrors.length() < maxOverflowErrors )
+        {
+          reportedErrors.push_back( tr( "Value '%1' has been trimmed (maximum field length: %2)" )
+                                    .arg( value, QString::number( mappedField.length() ) ) );
+        }
+        else if ( reportedErrors.length() == maxOverflowErrors )
+        {
+          reportedErrors.push_back( tr( "Only first %1 errors have been reported." )
+                                    .arg( maxOverflowErrors ) );
+        }
+      }
+
+      setRow( row, validValue, pair.second.toString() );
+
+      // Show errors if any
+      if ( !reportedErrors.isEmpty() )
+      {
+        mValueMapErrorsLabel->setVisible( true );
+        mValueMapErrorsLabel->setText( reportedErrors.join( QStringLiteral( "<br>" ) ) );
+      }
+    }
     ++row;
   }
 }
 
+QString QgsValueMapConfigDlg::checkValueLength( const QString &value )
+{
+  if ( layer()->fields().exists( field() ) )
+  {
+    const QgsField mappedField { layer()->fields().field( field() ) };
+    if ( mappedField.length() > 0 && value.length() > mappedField.length() )
+    {
+      return value.mid( 0, mappedField.length() );
+    }
+  }
+  return value;
+}
+
 void QgsValueMapConfigDlg::populateComboBox( QComboBox *comboBox, const QVariantMap &config, bool skipNull )
 {
   const QList<QVariant> valueList = config.value( QStringLiteral( "map" ) ).toList();
diff --git a/src/gui/editorwidgets/qgsvaluemapconfigdlg.h b/src/gui/editorwidgets/qgsvaluemapconfigdlg.h
index 947ecca17980..2cb7c4289357 100644
--- a/src/gui/editorwidgets/qgsvaluemapconfigdlg.h
+++ b/src/gui/editorwidgets/qgsvaluemapconfigdlg.h
@@ -78,6 +78,14 @@ class GUI_EXPORT QgsValueMapConfigDlg : public QgsEditorConfigWidget, private Ui
   private:
     void setRow( int row, const QString &value, const QString &description );
 
+    /**
+     * Validates a value against the maximum allowed field length and trims it is necessary.
+     * \param value
+     * \return the validated field value trimmed if necessary
+     */
+    QString checkValueLength( const QString &value );
+
+
   private slots:
     void copySelectionToClipboard();
     void vCellChanged( int row, int column );
diff --git a/src/ui/editorwidgets/qgsvaluemapconfigdlgbase.ui b/src/ui/editorwidgets/qgsvaluemapconfigdlgbase.ui
index e2d8c8612d40..caac3d79116b 100644
--- a/src/ui/editorwidgets/qgsvaluemapconfigdlgbase.ui
+++ b/src/ui/editorwidgets/qgsvaluemapconfigdlgbase.ui
@@ -14,7 +14,7 @@
    <string notr="true">Form</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="0" column="0" colspan="5">
+   <item row="0" column="0" colspan="3">
     <widget class="QLabel" name="valueMapLabel">
      <property name="text">
       <string>Combo box with predefined items. Value is stored in the attribute, description is shown in the combo box.</string>
@@ -31,66 +31,93 @@
      </property>
     </widget>
    </item>
-   <item row="1" column="4">
-    <spacer name="horizontalSpacer">
-     <property name="orientation">
-      <enum>Qt::Horizontal</enum>
-     </property>
-     <property name="sizeHint" stdset="0">
-      <size>
-       <width>339</width>
-       <height>20</height>
-      </size>
+   <item row="1" column="1">
+    <widget class="QPushButton" name="loadFromCSVButton">
+     <property name="text">
+      <string>Load Data from CSV File</string>
      </property>
-    </spacer>
-   </item>
-   <item row="2" column="0" colspan="5">
-    <widget class="QTableWidget" name="tableWidget">
-     <column>
-      <property name="text">
-       <string>Value</string>
-      </property>
-     </column>
-     <column>
-      <property name="text">
-       <string>Description</string>
-      </property>
-     </column>
     </widget>
    </item>
-   <item row="3" column="3" colspan="2">
-    <spacer name="horizontalSpacer_2">
+   <item row="1" column="2">
+    <spacer name="horizontalSpacer">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
-       <width>518</width>
+       <width>339</width>
        <height>20</height>
       </size>
      </property>
     </spacer>
    </item>
-   <item row="3" column="0">
-    <widget class="QPushButton" name="addNullButton">
-     <property name="text">
-      <string>Add &quot;NULL&quot; value</string>
-     </property>
-    </widget>
+   <item row="2" column="0" colspan="3">
+    <layout class="QVBoxLayout" name="verticalLayout">
+     <item>
+      <widget class="QTableWidget" name="tableWidget">
+       <column>
+        <property name="text">
+         <string>Value</string>
+        </property>
+       </column>
+       <column>
+        <property name="text">
+         <string>Description</string>
+        </property>
+       </column>
+      </widget>
+     </item>
+     <item>
+      <widget class="QLabel" name="mValueMapErrorsLabel">
+       <property name="enabled">
+        <bool>true</bool>
+       </property>
+       <property name="maximumSize">
+        <size>
+         <width>16777215</width>
+         <height>100</height>
+        </size>
+       </property>
+       <property name="text">
+        <string>No errors</string>
+       </property>
+       <property name="wordWrap">
+        <bool>true</bool>
+       </property>
+      </widget>
+     </item>
+    </layout>
    </item>
-   <item row="3" column="1">
-    <widget class="QPushButton" name="removeSelectedButton">
-     <property name="text">
-      <string>Remove Selected</string>
-     </property>
-    </widget>
-   </item>
-   <item row="1" column="1">
-    <widget class="QPushButton" name="loadFromCSVButton">
-     <property name="text">
-      <string>Load Data from CSV File</string>
-     </property>
-    </widget>
+   <item row="3" column="0" colspan="3">
+    <layout class="QHBoxLayout" name="horizontalLayout">
+     <item>
+      <widget class="QPushButton" name="addNullButton">
+       <property name="text">
+        <string>Add &quot;NULL&quot; value</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QPushButton" name="removeSelectedButton">
+       <property name="text">
+        <string>Remove Selected</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <spacer name="horizontalSpacer_2">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>518</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+    </layout>
    </item>
   </layout>
  </widget>