diff --git a/cmd/miqt-uic/constructors.go b/cmd/miqt-uic/constructors.go
index 312a10e..14ffcbf 100644
--- a/cmd/miqt-uic/constructors.go
+++ b/cmd/miqt-uic/constructors.go
@@ -1,165 +1,168 @@
 package main
 
-func constructorFunctionFor(className string) (string, bool) {
+func constructorFunctionFor(className string) string {
 
 	// Rebuild this list via:
-	//   grep -PRoh 'func New.+\(parent \*QWidget\)' ~/dev/miqt/qt/ | sed -re 's~^func New([^0-9]+)([0-9]*)\(.*~case "\1": return "New\1\2", true~'
+	//   grep -PRoh 'func New.+\(parent \*QWidget\)' ~/dev/miqt/qt/ | sed -re 's~^func New([^0-9]+)([0-9]*)\(.*~case "\1": return "New\1\2"~'
 
 	switch className {
 
 	// CODEGENERATED LIST START
 
 	case "QListWidget":
-		return "NewQListWidget2", true
+		return "NewQListWidget2"
 	case "QAbstractSpinBox":
-		return "NewQAbstractSpinBox2", true
+		return "NewQAbstractSpinBox2"
 	case "QStackedLayout":
-		return "NewQStackedLayout2", true
+		return "NewQStackedLayout2"
 	case "QColumnView":
-		return "NewQColumnView2", true
+		return "NewQColumnView2"
 	case "QProgressDialog":
-		return "NewQProgressDialog3", true
+		return "NewQProgressDialog3"
 	case "QTabWidget":
-		return "NewQTabWidget2", true
+		return "NewQTabWidget2"
 	case "QLabel":
-		return "NewQLabel3", true
+		return "NewQLabel3"
 	case "QKeySequenceEdit":
-		return "NewQKeySequenceEdit3", true
+		return "NewQKeySequenceEdit3"
 	case "QDockWidget":
-		return "NewQDockWidget5", true
+		return "NewQDockWidget5"
 	case "QFontComboBox":
-		return "NewQFontComboBox2", true
+		return "NewQFontComboBox2"
 	case "QTreeView":
-		return "NewQTreeView2", true
+		return "NewQTreeView2"
 	case "QCalendarWidget":
-		return "NewQCalendarWidget2", true
+		return "NewQCalendarWidget2"
 	case "QLineEdit":
-		return "NewQLineEdit3", true
+		return "NewQLineEdit3"
 	case "QMenuBar":
-		return "NewQMenuBar2", true
+		return "NewQMenuBar2"
 	case "QFrame":
-		return "NewQFrame2", true
+		return "NewQFrame2"
 	case "QAbstractScrollArea":
-		return "NewQAbstractScrollArea2", true
+		return "NewQAbstractScrollArea2"
 	case "QSplitter":
-		return "NewQSplitter3", true
+		return "NewQSplitter3"
 	case "QStackedWidget":
-		return "NewQStackedWidget2", true
+		return "NewQStackedWidget2"
 	case "QWizard":
-		return "NewQWizard2", true
+		return "NewQWizard2"
 	case "QWizardPage":
-		return "NewQWizardPage2", true
+		return "NewQWizardPage2"
 	case "QMdiSubWindow":
-		return "NewQMdiSubWindow2", true
+		return "NewQMdiSubWindow2"
 	case "QStatusBar":
-		return "NewQStatusBar2", true
+		return "NewQStatusBar2"
 	case "QToolButton":
-		return "NewQToolButton2", true
+		return "NewQToolButton2"
 	case "QShortcut":
-		return "NewQShortcut", true
+		return "NewQShortcut"
 	case "QSlider":
-		return "NewQSlider3", true
+		return "NewQSlider3"
 	case "QComboBox":
-		return "NewQComboBox2", true
+		return "NewQComboBox2"
 	case "QScrollBar":
-		return "NewQScrollBar3", true
+		return "NewQScrollBar3"
 	case "QTabBar":
-		return "NewQTabBar2", true
+		return "NewQTabBar2"
 	case "QTextBrowser":
-		return "NewQTextBrowser2", true
+		return "NewQTextBrowser2"
 	case "QTreeWidget":
-		return "NewQTreeWidget2", true
+		return "NewQTreeWidget2"
 	case "QDialog":
-		return "NewQDialog2", true
+		return "NewQDialog2"
 	case "QFormLayout":
-		return "NewQFormLayout2", true
+		return "NewQFormLayout2"
 	case "QToolBar":
-		return "NewQToolBar4", true
+		return "NewQToolBar4"
 	case "QWidget":
-		return "NewQWidget2", true
+		return "NewQWidget2"
 	case "QRadioButton":
-		return "NewQRadioButton3", true
+		return "NewQRadioButton3"
 	case "QCheckBox":
-		return "NewQCheckBox3", true
+		return "NewQCheckBox3"
 	case "QSizeGrip":
-		return "NewQSizeGrip", true
+		return "NewQSizeGrip"
 	case "QLCDNumber":
-		return "NewQLCDNumber3", true
+		return "NewQLCDNumber3"
 	case "QFileDialog":
-		return "NewQFileDialog3", true
+		return "NewQFileDialog3"
 	case "QUndoView":
-		return "NewQUndoView4", true
+		return "NewQUndoView4"
 	case "QGraphicsView":
-		return "NewQGraphicsView3", true
+		return "NewQGraphicsView3"
 	case "QPushButton":
-		return "NewQPushButton4", true
+		return "NewQPushButton4"
 	case "QColorDialog":
-		return "NewQColorDialog3", true
+		return "NewQColorDialog3"
 	case "QMessageBox":
-		return "NewQMessageBox4", true
+		return "NewQMessageBox4"
 	case "QSplashScreen":
-		return "NewQSplashScreen3", true
+		return "NewQSplashScreen3"
 	case "QErrorMessage":
-		return "NewQErrorMessage2", true
+		return "NewQErrorMessage2"
 	case "QListView":
-		return "NewQListView2", true
+		return "NewQListView2"
 	case "QDateTimeEdit":
-		return "NewQDateTimeEdit5", true
+		return "NewQDateTimeEdit5"
 	case "QTimeEdit":
-		return "NewQTimeEdit3", true
+		return "NewQTimeEdit3"
 	case "QDateEdit":
-		return "NewQDateEdit3", true
+		return "NewQDateEdit3"
 	case "QMenu":
-		return "NewQMenu3", true
+		return "NewQMenu3"
 	case "QToolBox":
-		return "NewQToolBox2", true
+		return "NewQToolBox2"
 	case "QTableWidget":
-		return "NewQTableWidget3", true
+		return "NewQTableWidget3"
 	case "QFocusFrame":
-		return "NewQFocusFrame2", true
+		return "NewQFocusFrame2"
 	case "QHBoxLayout":
-		return "NewQHBoxLayout2", true
+		return "NewQHBoxLayout2"
 	case "QVBoxLayout":
-		return "NewQVBoxLayout2", true
+		return "NewQVBoxLayout2"
 	case "QInputDialog":
-		return "NewQInputDialog2", true
+		return "NewQInputDialog2"
 	case "QTableView":
-		return "NewQTableView2", true
+		return "NewQTableView2"
 	case "QMdiArea":
-		return "NewQMdiArea2", true
+		return "NewQMdiArea2"
 	case "QSpinBox":
-		return "NewQSpinBox2", true
+		return "NewQSpinBox2"
 	case "QDoubleSpinBox":
-		return "NewQDoubleSpinBox2", true
+		return "NewQDoubleSpinBox2"
 	case "QProgressBar":
-		return "NewQProgressBar2", true
+		return "NewQProgressBar2"
 	case "QTextEdit":
-		return "NewQTextEdit3", true
+		return "NewQTextEdit3"
 	case "QAbstractSlider":
-		return "NewQAbstractSlider2", true
+		return "NewQAbstractSlider2"
 	case "QDialogButtonBox":
-		return "NewQDialogButtonBox5", true
+		return "NewQDialogButtonBox5"
 	case "QFontDialog":
-		return "NewQFontDialog3", true
+		return "NewQFontDialog3"
 	case "QMainWindow":
-		return "NewQMainWindow2", true
+		return "NewQMainWindow2"
 	case "QCommandLinkButton":
-		return "NewQCommandLinkButton4", true
+		return "NewQCommandLinkButton4"
 	case "QDial":
-		return "NewQDial2", true
+		return "NewQDial2"
 	case "QGridLayout":
-		return "NewQGridLayout", true
+		return "NewQGridLayout"
 	case "QPlainTextEdit":
-		return "NewQPlainTextEdit3", true
+		return "NewQPlainTextEdit3"
 	case "QScrollArea":
-		return "NewQScrollArea2", true
+		return "NewQScrollArea2"
 	case "QGroupBox":
-		return "NewQGroupBox3", true
+		return "NewQGroupBox3"
 
 	// CODEGENERATED LIST END
 
 	default:
-		return "", false
+		// This class is not known to miqt-uic
+		// Assume it's a user promoted type from Qt Designer with a matching ctor
+		// of the form New{Class}(parent *QWidget)
+		return "New" + className
 
 	}
 
diff --git a/cmd/miqt-uic/ui2go.go b/cmd/miqt-uic/ui2go.go
index 2075e7f..7180c58 100644
--- a/cmd/miqt-uic/ui2go.go
+++ b/cmd/miqt-uic/ui2go.go
@@ -61,10 +61,7 @@ func normalizeEnumName(s string) string {
 func generateWidget(w UiWidget, parentName string, parentClass string) (string, error) {
 	ret := strings.Builder{}
 
-	ctor, ok := constructorFunctionFor(w.Class)
-	if !ok {
-		return "", fmt.Errorf("No known widget constructor function for %q class %q", w.Name, w.Class)
-	}
+	ctor := constructorFunctionFor(w.Class)
 
 	ret.WriteString(`
 	ui.` + w.Name + ` = qt.` + ctor + `(` + qwidgetName(parentName, parentClass) + `)
@@ -122,10 +119,7 @@ func generateWidget(w UiWidget, parentName string, parentClass string) (string,
 
 	// Layout
 	if w.Layout != nil {
-		ctor, ok := constructorFunctionFor(w.Layout.Class)
-		if !ok {
-			return "", fmt.Errorf("No known layout constructor function for %q class %q", w.Layout.Name, w.Layout.Class)
-		}
+		ctor := constructorFunctionFor(w.Layout.Class)
 
 		ret.WriteString(`
 		ui.` + w.Layout.Name + ` = qt.` + ctor + `(` + qwidgetName("ui."+w.Name, w.Class) + `)