diff --git a/doc/fixes36.1 b/doc/fixes36.1
index 02bded2af..c282bdc58 100644
--- a/doc/fixes36.1
+++ b/doc/fixes36.1
@@ -635,6 +635,8 @@ unix: race condition with parallel make: src/Makefile might start building
 unix: Makefile.{src,utl} ignored CPPFLAGS which is expanded by the default .c
 	rule by GNU make so if user had a value for that in the environment,
 	it would apply to some files but not others; explicitly override it
+unix: enable code guarded by USE_WIN_IOCTL by default unless prevented by
+	uncommenting #define AVOID_WIN_IOCTL in include/unixconf.h
 win32gui: getversionstring() was overflowing the provided Help About buffer
 win32gui: guard against buffer overflow in in mswin_getlin()
 win32gui: handle menu_color attribute
diff --git a/include/unixconf.h b/include/unixconf.h
index 88e309d55..cec8c709a 100644
--- a/include/unixconf.h
+++ b/include/unixconf.h
@@ -1,4 +1,4 @@
-/* NetHack 3.6	unixconf.h	$NHDT-Date: 1451342112 2015/12/28 22:35:12 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.25 $ */
+/* NetHack 3.6	unixconf.h	$NHDT-Date: 1520099325 2018/03/03 17:48:45 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.30 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -136,6 +136,8 @@
 #define TIMED_DELAY
 #endif
 
+/* #define AVOID_WIN_IOCTL */ /* ensure USE_WIN_IOCTL remains undefined */
+
 /*
  * If you define MAIL, then the player will be notified of new mail
  * when it arrives.  If you also define DEF_MAILREADER then this will
diff --git a/sys/share/ioctl.c b/sys/share/ioctl.c
index 3da74b81a..138d02b5c 100644
--- a/sys/share/ioctl.c
+++ b/sys/share/ioctl.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	ioctl.c	$NHDT-Date: 1432512788 2015/05/25 00:13:08 $  $NHDT-Branch: master $:$NHDT-Revision: 1.12 $ */
+/* NetHack 3.6	ioctl.c	$NHDT-Date: 1520099308 2018/03/03 17:48:28 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.13 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -63,9 +63,12 @@ struct termio termio;
 #include <signal.h>
 #endif
 
-#if defined(TIOCGWINSZ)                                    \
-    && (defined(BSD) || defined(ULTRIX) || defined(AIX_31) \
-        || defined(_BULL_SOURCE) || defined(SVR4))
+/* AVOID_WIN_IOCTL can be uncommented in unixconf.h
+ * to force USE_WIN_IOTCL to remain undefined,
+ * instead of the restricted explicit opt-in
+ * logic that used to be here.
+ */
+#if defined(TIOCGWINSZ) && !defined(AVOID_WIN_IOCTL)
 #define USE_WIN_IOCTL
 #include "tcap.h" /* for LI and CO */
 #endif