diff --git a/gui.cc b/gui.cc
index 1d15e6f..b70a87f 100644
--- a/gui.cc
+++ b/gui.cc
@@ -67,7 +67,7 @@ void displayerror (std::string error) {
 			 GTK_DIALOG_DESTROY_WITH_PARENT,
 			 GTK_MESSAGE_ERROR,
 			 GTK_BUTTONS_OK,
-			 error.c_str());
+			 "%s", error.c_str());
 	gtk_window_set_title(GTK_WINDOW(dialog), "Error");
 	gtk_dialog_run(GTK_DIALOG(dialog));
 	gtk_widget_destroy(dialog);
diff --git a/main.cc b/main.cc
index c59def6..9b80b7d 100644
--- a/main.cc
+++ b/main.cc
@@ -44,6 +44,10 @@ int main (int argc, char **argv) {
 	//
 
 	window = gtk_builder_get_object (builder, "window-main");
+	if(window == NULL) {
+	  printf("ERROR: gtk_builder_get_object() failed\n");
+	  return 1;
+	}
 	gtk_widget_show_all (GTK_WIDGET(window));
 
 	gtk_main ();
diff --git a/simpleskycam.ui b/simpleskycam.ui
index a3c3789..bda9c7b 100644
--- a/simpleskycam.ui
+++ b/simpleskycam.ui
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- Generated with glade 3.38.2 -->
 <interface>
-  <requires lib="gtk+" version="3.24"/>
+  <requires lib="gtk+" version="3.18"/>
   <object class="GtkAdjustment" id="detect-adj-bright">
     <property name="upper">255.99</property>
     <property name="value">50</property>