Index: Makefile
===================================================================
--- Makefile	(revision 0d0b3197a149bb5e5c53d21136df5b8c283cdc4a)
+++ Makefile	(revision 3c7702c05cfce1577b9b1bb89cfe61f809c024db)
@@ -93,4 +93,11 @@
 endif
 
+# `sed` pulls a list of "compatibility-only" error codes from `errno.in`,
+# the following grep finds instances of those error codes in HelenOS code.
+check_errno:
+	@ ! cat abi/include/abi/errno.in | \
+	sed -n -e '1,/COMPAT_START/d' -e 's/__errno_entry(\([A-Z0-9]\+\).*/\\b\1\\b/p' | \
+	git grep -n -f - -- ':(exclude)abi' ':(exclude)uspace/lib/posix'
+
 # Autotool (detects compiler features)
 
Index: abi/include/abi/errno.h
===================================================================
--- abi/include/abi/errno.h	(revision 0d0b3197a149bb5e5c53d21136df5b8c283cdc4a)
+++ abi/include/abi/errno.h	(revision 3c7702c05cfce1577b9b1bb89cfe61f809c024db)
@@ -57,4 +57,6 @@
  */
 
+/* COMPAT_START -- do not remove or edit this comment */
+
 #define E2BIG             __errno_t(  101)
 #define EACCES            __errno_t(  102)
Index: abi/include/abi/errno.in
===================================================================
--- abi/include/abi/errno.in	(revision 0d0b3197a149bb5e5c53d21136df5b8c283cdc4a)
+++ abi/include/abi/errno.in	(revision 3c7702c05cfce1577b9b1bb89cfe61f809c024db)
@@ -55,4 +55,6 @@
  * move it up to the first group.
  */
+
+/* COMPAT_START -- do not remove or edit this comment */
 
 __errno_entry(E2BIG            ,  101, "Argument list too long")
Index: uspace/srv/net/inetsrv/ntrans.c
===================================================================
--- uspace/srv/net/inetsrv/ntrans.c	(revision 0d0b3197a149bb5e5c53d21136df5b8c283cdc4a)
+++ uspace/srv/net/inetsrv/ntrans.c	(revision 3c7702c05cfce1577b9b1bb89cfe61f809c024db)
@@ -153,5 +153,5 @@
  *
  * @return EOK if woken up by another fibril
- * @return ETIMEDOUT if timed out
+ * @return ETIMEOUT if timed out
  *
  */