diff --git a/src/core/qgsattributetableconfig.cpp b/src/core/qgsattributetableconfig.cpp
index 6f77738daf7..71af24c4676 100644
--- a/src/core/qgsattributetableconfig.cpp
+++ b/src/core/qgsattributetableconfig.cpp
@@ -197,7 +197,8 @@ void QgsAttributeTableConfig::readXml( const QDomNode &node )
   }
 
   mSortExpression = configNode.toElement().attribute( QStringLiteral( "sortExpression" ) );
-  mSortOrder = static_cast<Qt::SortOrder>( configNode.toElement().attribute( QStringLiteral( "sortOrder" ) ).toInt() );
+  Qt::SortOrder sortOrder = static_cast<Qt::SortOrder>( configNode.toElement().attribute( QStringLiteral( "sortOrder" ) ).toInt() );
+  setSortOrder( sortOrder );
 }
 
 QString QgsAttributeTableConfig::sortExpression() const
@@ -242,6 +243,12 @@ Qt::SortOrder QgsAttributeTableConfig::sortOrder() const
 
 void QgsAttributeTableConfig::setSortOrder( Qt::SortOrder sortOrder )
 {
+  // fix https://hub.qgis.org/issues/15803
+  if ( sortOrder != Qt::AscendingOrder && sortOrder != Qt::DescendingOrder )
+  {
+    sortOrder = Qt::AscendingOrder;
+  }
+
   mSortOrder = sortOrder;
 }
 
diff --git a/src/gui/attributetable/qgsattributetablefiltermodel.cpp b/src/gui/attributetable/qgsattributetablefiltermodel.cpp
index 2cef733ec17..465b751b2d4 100644
--- a/src/gui/attributetable/qgsattributetablefiltermodel.cpp
+++ b/src/gui/attributetable/qgsattributetablefiltermodel.cpp
@@ -64,6 +64,9 @@ bool QgsAttributeTableFilterModel::lessThan( const QModelIndex &left, const QMod
 
 void QgsAttributeTableFilterModel::sort( int column, Qt::SortOrder order )
 {
+  if ( order != Qt::AscendingOrder && order != Qt::DescendingOrder )
+    order = Qt::AscendingOrder;
+
   int myColumn = mColumnMapping.at( column );
   masterModel()->prefetchColumnData( myColumn );
   QSortFilterProxyModel::sort( myColumn, order );
@@ -211,6 +214,9 @@ void QgsAttributeTableFilterModel::setAttributeTableConfig( const QgsAttributeTa
 
 void QgsAttributeTableFilterModel::sort( const QString &expression, Qt::SortOrder order )
 {
+  if ( order != Qt::AscendingOrder && order != Qt::DescendingOrder )
+    order = Qt::AscendingOrder;
+
   QSortFilterProxyModel::sort( -1 );
   masterModel()->prefetchSortData( expression );
   QSortFilterProxyModel::sort( 0, order ) ;
@@ -226,11 +232,17 @@ void QgsAttributeTableFilterModel::setSelectedOnTop( bool selectedOnTop )
   if ( mSelectedOnTop != selectedOnTop )
   {
     mSelectedOnTop = selectedOnTop;
+    int column = sortColumn();
+    Qt::SortOrder order = sortOrder();
 
-    if ( sortColumn() == -1 )
-    {
-      sort( 0 );
-    }
+    // set default sort values if they are not correctly set
+    if ( column < 0 )
+      column = 0;
+
+    if ( order != Qt::AscendingOrder && order != Qt::DescendingOrder )
+      order = Qt::AscendingOrder;
+
+    sort( column, order );
     invalidate();
   }
 }