[gtkada] Problem using Gtk_Label

[Roger Mc Murtrie]

Mac OSX 10.11.3
GPS 6.1.1 (20150118) hosted on x86_64-apple-darwin12.5.0
GNAT GPL 2015 (20150428-49)
gtkada-gpl-2015-src

Im trying to use labels under GtkAda  but the following declaration and assignment in my program compiles and builds OK.
aLabel	: Gtk_Label;

aLabel := gtk_label_new;
 with no other references to aLabel.

When I run the program it crashes with:
(process:10666): GLib-GObject-CRITICAL **: g_object_get_qdata: assertion 'G_IS_OBJECT (object)' failed

(process:10666): GLib-GObject-CRITICAL **: g_object_set_qdata_full: assertion 'G_IS_OBJECT (object)' failed
An exception occurred in Show_AdaQuant_Dialog.
Exception name: CONSTRAINT_ERROR
Message: erroneous memory access

Any advice will be appreciated.
Regards,
Roger