Index: uspace/lib/c/include/errno.h
===================================================================
--- uspace/lib/c/include/errno.h	(revision 27b85d9ebdc66e9e29d0e2194cb70e62a1180a40)
+++ uspace/lib/c/include/errno.h	(revision 1866945c7da7a2ddfebcb5abd73e1b4f8cd1c987)
@@ -65,4 +65,7 @@
 #define EEMPTY (-302)
 
+/** Negative acknowledgment. */
+#define ENAK (-303)
+
 /** An API function is called while another blocking function is in progress. */
 #define EINPROGRESS  (-10036)