diff --git a/gtk/gtkfontchooser.c b/gtk/gtkfontchooser.c
index bc86b8148b..8a98b1e027 100644
--- a/gtk/gtkfontchooser.c
+++ b/gtk/gtkfontchooser.c
@@ -1535,6 +1535,7 @@ gtk_font_selection_set_font_name (GtkFontSelection *fontsel,
   gboolean              found = FALSE;
   
   g_return_val_if_fail (GTK_IS_FONT_SELECTION (fontsel), FALSE);
+  g_return_val_if_fail (fontname != NULL, FALSE);
 
   if (!gtk_widget_has_screen (GTK_WIDGET (fontsel)))
     return FALSE;