diff --git a/configure.ac b/configure.ac
index f1bff955..2ad3675b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,6 +48,12 @@ AC_ARG_WITH([gssapi],
   [],
   [with_gssapi=yes])
 
+AC_ARG_WITH([quartz],
+  [AS_HELP_STRING([--with-quartz],
+                  [build for the MacOS Quartz GTK back end])],
+  [AC_DEFINE([OSX_GTK], [1], [Define if building with GTK for MacOS.])],
+  [])
+
 WITH_GSSAPI=
 AS_IF([test "x$with_gssapi" != xno],
   [AC_DEFINE([WITH_GSSAPI], [1], [Define if building with GSSAPI support.])])
diff --git a/unix/gtkdlg.c b/unix/gtkdlg.c
index c044c062..23e9f465 100644
--- a/unix/gtkdlg.c
+++ b/unix/gtkdlg.c
@@ -6,26 +6,27 @@
 #include <stdarg.h>
 #include <ctype.h>
 #include <time.h>
+
 #include <gtk/gtk.h>
 #if !GTK_CHECK_VERSION(3,0,0)
 #include <gdk/gdkkeysyms.h>
 #endif
+
+#include "putty.h"
+#include "gtkcompat.h"
+#include "gtkcols.h"
+#include "gtkfont.h"
+
 #ifndef NOT_X_WINDOWS
 #include <gdk/gdkx.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #endif
 
-#include "gtkcompat.h"
-
-#include "gtkcols.h"
-#include "gtkfont.h"
-
 #ifdef TESTMODE
 #define PUTTY_DO_GLOBALS	       /* actually _define_ globals */
 #endif
 
-#include "putty.h"
 #include "storage.h"
 #include "dialog.h"
 #include "tree234.h"
diff --git a/unix/gtkfont.c b/unix/gtkfont.c
index a43363b9..1a9860ab 100644
--- a/unix/gtkfont.c
+++ b/unix/gtkfont.c
@@ -12,22 +12,24 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
+
 #include <gtk/gtk.h>
 #if !GTK_CHECK_VERSION(3,0,0)
 #include <gdk/gdkkeysyms.h>
 #endif
-#ifndef NOT_X_WINDOWS
-#include <gdk/gdkx.h>
-#include <X11/Xlib.h>
-#include <X11/Xutil.h>
-#include <X11/Xatom.h>
-#endif
 
 #include "putty.h"
 #include "gtkfont.h"
 #include "gtkcompat.h"
 #include "tree234.h"
 
+#ifndef NOT_X_WINDOWS
+#include <gdk/gdkx.h>
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#include <X11/Xatom.h>
+#endif
+
 /*
  * Future work:
  * 
diff --git a/unix/gtkwin.c b/unix/gtkwin.c
index f6befeed..69535c36 100644
--- a/unix/gtkwin.c
+++ b/unix/gtkwin.c
@@ -22,12 +22,6 @@
 #if !GTK_CHECK_VERSION(3,0,0)
 #include <gdk/gdkkeysyms.h>
 #endif
-#ifndef NOT_X_WINDOWS
-#include <gdk/gdkx.h>
-#include <X11/Xlib.h>
-#include <X11/Xutil.h>
-#include <X11/Xatom.h>
-#endif
 
 #if GTK_CHECK_VERSION(2,0,0)
 #include <gtk/gtkimmodule.h>
@@ -42,6 +36,13 @@
 #include "gtkcompat.h"
 #include "gtkfont.h"
 
+#ifndef NOT_X_WINDOWS
+#include <gdk/gdkx.h>
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#include <X11/Xatom.h>
+#endif
+
 #define CAT2(x,y) x ## y
 #define CAT(x,y) CAT2(x,y)
 #define ASSERT(x) enum {CAT(assertion_,__LINE__) = 1 / (x)}
diff --git a/unix/unix.h b/unix/unix.h
index fbe025ba..90922451 100644
--- a/unix/unix.h
+++ b/unix/unix.h
@@ -12,6 +12,20 @@
 #endif /*  NO_LIBDL */
 #include "charset.h"
 
+#ifdef OSX_GTK
+/*
+ * Assorted tweaks to various parts of the GTK front end which all
+ * need to be enabled when compiling on OS X. Because I might need the
+ * same tweaks on other systems in future, I don't want to
+ * conditionalise all of them on OSX_GTK directly, so instead, each
+ * one has its own name and we enable them all centrally here if
+ * OSX_GTK is defined at configure time.
+ */
+#define NOT_X_WINDOWS /* of course, all the X11 stuff should be disabled */
+#define NO_PTY_PRE_INIT /* OS X gets very huffy if we try to set[ug]id */
+#define SET_NONBLOCK_VIA_OPENPT /* work around missing fcntl functionality */
+#endif
+
 struct Filename {
     char *path;
 };