diff --git a/src/gui/editorwidgets/qgsrelationreferencewidget.cpp b/src/gui/editorwidgets/qgsrelationreferencewidget.cpp
index 8582613316e..8873197c32c 100644
--- a/src/gui/editorwidgets/qgsrelationreferencewidget.cpp
+++ b/src/gui/editorwidgets/qgsrelationreferencewidget.cpp
@@ -365,7 +365,11 @@ QVariant QgsRelationReferenceWidget::foreignKey()
   }
   else
   {
-    if ( !mFeature.isValid() )
+    if ( mReferencingFieldIdx < 0 || mReferencingFieldIdx >= mReferencingLayer->fields().count() )
+    {
+      return QVariant();
+    }
+    else if ( !mFeature.isValid() )
     {
       return QVariant( mReferencingLayer->fields().at( mReferencingFieldIdx ).type() );
     }