Trouble findin a library which *is* installed

I downloaded some code as an example of using Cairo with Gdk from the web page http://www.donadeo.net/post/2008/draw-something-on-the-screen-and-interact-with-it.

I try to compile it:

endrik@notlookedfor:~/dv/fun/group/toy/cairo_toy$ ocamlfind ocamlopt -package gdkEvent toy_maker.mli toy_maker.ml my_interactor.ml demo_toy.ml -o runme
ocamlfind: Package `gdkEvent' not found
hendrik@notlookedfor:~/dv/fun/group/toy/cairo_toy$

Evidently, there's trouble finding gdkEvent.

But the files do exist on my system, as installed from the Debian Jessie package liblablgtk2-ocaml-dev:

hendrik@notlookedfor:~/dv/fun/group/toy/cairo_toy$ locate -i gdkevent
/usr/include/gtk-2.0/gdk/gdkevents.h
/usr/include/gtk-3.0/gdk/gdkevents.h
/usr/lib/ocaml/lablgtk2/gdkEvent.cmi
/usr/lib/ocaml/lablgtk2/gdkEvent.cmx
/usr/lib/ocaml/lablgtk2/gdkEvent.ml
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Button.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Client.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Configure.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Crossing.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Expose.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Focus.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Key.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Motion.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Property.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Proximity.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Scroll.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Selection.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Setting.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.Visibility.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.WindowState.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/GdkEvent.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Button.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Client.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Configure.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Crossing.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Expose.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Focus.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Key.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Motion.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Property.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Proximity.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Scroll.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Selection.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Setting.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.Visibility.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.WindowState.html
/usr/share/doc/liblablgtk2-ocaml-doc/html/api/type_GdkEvent.html
hendrik@notlookedfor:~/dv/fun/group/toy/cairo_toy$ 

Yet nocalfind does not find them:

hendrik@notlookedfor:~$ ocamlfind list
bigarray            (version: [distributed with Ocaml])
cairo2              (version: 0.4.6)
camlp4              (version: [distributed with Ocaml])
camlp4.exceptiontracer (version: [distributed with Ocaml])
camlp4.extend       (version: [distributed with Ocaml])
camlp4.foldgenerator (version: [distributed with Ocaml])
camlp4.fulllib      (version: [distributed with Ocaml])
camlp4.gramlib      (version: [distributed with Ocaml])
camlp4.lib          (version: [distributed with Ocaml])
camlp4.listcomprehension (version: [distributed with Ocaml])
camlp4.locationstripper (version: [distributed with Ocaml])
camlp4.macro        (version: [distributed with Ocaml])
camlp4.mapgenerator (version: [distributed with Ocaml])
camlp4.metagenerator (version: [distributed with Ocaml])
camlp4.profiler     (version: [distributed with Ocaml])
camlp4.quotations   (version: [distributed with Ocaml])
camlp4.quotations.o (version: [distributed with Ocaml])
camlp4.quotations.r (version: [distributed with Ocaml])
camlp4.tracer       (version: [distributed with Ocaml])
compiler-libs       (version: [distributed with Ocaml])
compiler-libs.bytecomp (version: [distributed with Ocaml])
compiler-libs.common (version: [distributed with Ocaml])
compiler-libs.optcomp (version: [distributed with Ocaml])
compiler-libs.toplevel (version: [distributed with Ocaml])
dynlink             (version: [distributed with Ocaml])
findlib             (version: 1.4)
glMLite             (version: 0.03.51)
glMLite.ftgl        (version: n/a)
glMLite.fungl       (version: n/a)
glMLite.funglut     (version: n/a)
glMLite.genimg_loader (version: n/a)
glMLite.gle         (version: n/a)
glMLite.glu         (version: n/a)
glMLite.glut        (version: n/a)
glMLite.jpeg_loader (version: n/a)
glMLite.png_loader  (version: n/a)
glMLite.svg_loader  (version: n/a)
glMLite.vbo         (version: n/a)
glMLite.vertex_arrays (version: n/a)
graphics            (version: [distributed with Ocaml])
labltk              (version: [distributed with Ocaml])
num                 (version: [distributed with Ocaml])
num-top             (version: 1.4)
num.core            (version: [internal])
ocamlbuild          (version: [distributed with Ocaml])
stdlib              (version: [distributed with Ocaml])
str                 (version: [distributed with Ocaml])
threads             (version: [distributed with Ocaml])
threads.posix       (version: [internal])
threads.vm          (version: [internal])
unix                (version: [distributed with Ocaml])
hendrik@notlookedfor:~$ 


How do I goo about getting ocamlfind to find these files?
Is it a bug in ocamlfind?
Is there some configuration needed for ocamlfind?
Should the Debian package for lablgtk do that configuration in a postinstall?
Or am I dong it all copletely wrong?

-- hendrik