diff --git a/src/streams/gray/fd-mixin.lisp b/src/streams/gray/fd-mixin.lisp
index 1ba6081613b98d81d216f7e73abdf109811cc7b3..52d35e8240a0175b233e379cee756306e483b291 100644
--- a/src/streams/gray/fd-mixin.lisp
+++ b/src/streams/gray/fd-mixin.lisp
@@ -21,10 +21,10 @@
 ;;;; Get and Set O_NONBLOCK
 
 (defmethod fd-non-blocking ((fd-mixin dual-channel-fd-mixin))
-  (isys:fd-nonblock (fd-of fd-mixin)))
+  (isys:fd-nonblock-p (fd-of fd-mixin)))
 (defobsolete fd-non-blocking "stream FDs are now always non-blocking.")
 
 (defmethod (setf fd-non-blocking) (mode (fd-mixin dual-channel-fd-mixin))
   (check-type mode boolean "a boolean value")
-  (setf (isys:fd-nonblock (fd-of fd-mixin)) mode))
+  (setf (isys:fd-nonblock-p (fd-of fd-mixin)) mode))
 (defobsolete (setf fd-non-blocking) "stream FDs are now always non-blocking.")