diff --git a/configure.in b/configure.in
index 7a225c361..57bd8197f 100644
--- a/configure.in
+++ b/configure.in
@@ -46,13 +46,8 @@ case $host_os in
         if test "x$with_archflags" != x ; then
             CFLAGS="$CFLAGS $with_archflags"
         fi
-        USEMMFILES="Yes"
-        ;;
-    *)
-        USEMMFILES="No"
         ;;
 esac
-AC_SUBST(USEMMFILES)
 
 dnl FLTK library versions...
 FL_MAJOR_VERSION=1
@@ -73,13 +68,13 @@ AC_SUBST(ARCHFLAGS)
 AC_SUBST(OPTIM)
 
 dnl OS-specific pre-tests...
-dnl host_os_gui equals $host_os unless we target Cygwin in combination with X11.
+dnl host_os_gui equals $host_os unless we target Cygwin or Darwin in combination with X11.
 host_os_gui=$host_os
 case $host_os in
     cygwin*)
         # Handle Cygwin option *first*, before all other tests.
 	AC_ARG_ENABLE(cygwin, [  --enable-cygwin         use the Cygwin libraries [[default=no]]])
-	AC_ARG_ENABLE(x11,    [  --enable-x11            use Cygwin with X11 [[default=no]]])
+	AC_ARG_ENABLE(x11,    [  --enable-x11            use with X11 [[default=no]]])
 	if test x$enable_cygwin = xyes; then
 	    # we target Cygwin in combination with X11
 	    if test x$enable_x11 = xyes; then
@@ -87,6 +82,14 @@ case $host_os in
 	    fi
 	fi
 	;;
+    darwin*)
+	if test x$enable_x11 = xyes; then
+		host_os_gui="X11"
+		OPTIM="-U__APPLE__ $OPTIM"
+	fi
+	;;
+   *)
+   ;;
 esac
 
 dnl Define the libraries and link options we will need.
@@ -397,12 +400,6 @@ AC_ARG_WITH(archflags, [  --with-archflags="flags"
                           use custom architecture flags 
 			  (possible Mac OS X values include -arch i386, -arch x86_64, -arch ppc)],
     ARCHFLAGS="$withval")
-case $host_os in
-    darwin*)
-# QD is not supported anymore since 1.3
-	AC_DEFINE(__APPLE_QUARTZ__)
-	;;
-esac
 
 dnl Find commands...
 AC_PROG_INSTALL
@@ -832,6 +829,8 @@ AC_ARG_WITH(links, [  --with-links            make header links for common missp
 INSTALL_DESKTOP=""
 UNINSTALL_DESKTOP=""
 
+USEMMFILES="No"
+
 case $host_os_gui in
     cygwin* | mingw*)
 	dnl Cygwin environment, using windows GDI ...
@@ -878,6 +877,10 @@ case $host_os_gui in
 	;;
 
     darwin*)
+	AC_DEFINE(__APPLE_QUARTZ__)
+
+        USEMMFILES="Yes"
+
         # MacOS X uses Cocoa for graphics.
         LIBS="$LIBS -framework Cocoa"
 
@@ -1090,6 +1093,8 @@ AC_SUBST(THREADS)
 AC_SUBST(INSTALL_DESKTOP)
 AC_SUBST(UNINSTALL_DESKTOP)
 
+AC_SUBST(USEMMFILES)
+
 dnl Figure out the appropriate formatted man page extension...
 case "$host_os" in
     *bsd* | darwin*)