diff --git a/src/ATC/atcdialog.cxx b/src/ATC/atcdialog.cxx
index f2e851e26..ba7bc1791 100644
--- a/src/ATC/atcdialog.cxx
+++ b/src/ATC/atcdialog.cxx
@@ -248,6 +248,10 @@ void FGATCDialogNew::update(double dt) {
 
     const char *dialog_name = "atc-dialog";
     _gui = (NewGUI *)globals->get_subsystem("gui");
+    if (!_gui) {
+      return;
+    }
+  
     SGPropertyNode_ptr dlg = _gui->getDialogProperties(dialog_name);
     if (!dlg)
         return;
diff --git a/src/Main/fg_commands.cxx b/src/Main/fg_commands.cxx
index f9efa5b47..5611cbf10 100644
--- a/src/Main/fg_commands.cxx
+++ b/src/Main/fg_commands.cxx
@@ -1022,7 +1022,10 @@ static bool
 do_dialog_new (const SGPropertyNode * arg)
 {
     NewGUI * gui = (NewGUI *)globals->get_subsystem("gui");
-
+    if (!gui) {
+      return false;
+    }
+  
     // Note the casting away of const: this is *real*.  Doing a
     // "dialog-apply" command later on will mutate this property node.
     // I'm not convinced that this isn't the Right Thing though; it