diff --git a/src/proto.h b/src/proto.h
index 4c52d4b..77ea826 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -194,6 +194,7 @@
 #  endif
 #  ifdef FEAT_GUI_MOTIF
 #   include "gui_motif.pro"
+#   include "gui_xmdlg.pro"
 #  endif
 #  ifdef FEAT_GUI_ATHENA
 #   include "gui_athena.pro"