diff --git a/src/frontends/qt4/GuiDelimiter.h b/src/frontends/qt4/GuiDelimiter.h
index 7bd6ee610b..fb0c0bc64f 100644
--- a/src/frontends/qt4/GuiDelimiter.h
+++ b/src/frontends/qt4/GuiDelimiter.h
@@ -16,6 +16,8 @@
 
 #include "ui_DelimiterUi.h"
 
+#include "support/docstring.h"
+
 class QListWidgetItem;
 
 namespace lyx {