Index: gtk/Makefile
==================================================================
--- gtk/Makefile
+++ gtk/Makefile
@@ -1,14 +1,14 @@
 PREFIX ?= /usr/local
 
 all:
-	@objfw-compile -Wall -g --lib 0.0 -o objgui -I../headers \
+	@objfw-compile -DOG_GTK -Wall -g --lib 0.0 -o objgui -I../headers \
 		`pkg-config --cflags --libs gtk+-3.0` \
 		`ls *.m | fgrep -v test.m`
 
 test:
-	@objfw-compile -Wall -g -o test -I../headers \
+	@objfw-compile -DOG_GTK -Wall -g -o test -I../headers \
 		`pkg-config --cflags --libs gtk+-3.0` \
 		*.m
 
 install:
 	mkdir -p ${PREFIX}/include/ObjGUI

Index: headers/OGApplication.h
==================================================================
--- headers/OGApplication.h
+++ headers/OGApplication.h
@@ -1,7 +1,5 @@
-#include <gtk/gtk.h>
-
 #import <ObjFW/ObjFW.h>
 
 @protocol OGApplicationDelegate <OFObject>
 - (void)applicationDidFinishLaunching;
 @optional

Index: headers/OGWidget.h
==================================================================
--- headers/OGWidget.h
+++ headers/OGWidget.h
@@ -18,20 +18,24 @@
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <gtk/gtk.h>
+#ifdef OG_GTK
+# include <gtk/gtk.h>
+#endif
 
 #import <ObjFW/ObjFW.h>
 
 @interface OGWidget: OFObject
 {
 @public
+#ifdef OG_GTK
 	GtkWidget *widget;
+#endif
 }
 
 - (void)show;
 - (void)hide;
 @end
 
 extern void og_destroy(GtkWidget*, OGWidget*);