diff --git a/doc/zmq_setsockopt.txt b/doc/zmq_setsockopt.txt
index 2928397a..018070d0 100644
--- a/doc/zmq_setsockopt.txt
+++ b/doc/zmq_setsockopt.txt
@@ -371,11 +371,8 @@ ZMQ_ROUTER_MANDATORY: accept only routable messages on ROUTER sockets
 
 Sets the 'ROUTER' socket behavior when an unroutable message is encountered. A 
 value of `0` is the default and discards the message silently when it cannot be 
-routed.  A value of `1` returns an 'EAGAIN' error code if the message cannot be 
-routed.
-
-Note: Setting this socket option may have unpredictable effects on reactor-type 
-libraries that assume EAGAIN will only be sent in HWM-type situations. 
+routed.  A value of `1` returns an 'EHOSTUNREACH' error code if the message
+cannot be routed.
 
 [horizontal]
 Option value type:: int
diff --git a/src/router.cpp b/src/router.cpp
index fdba1f82..c136e607 100644
--- a/src/router.cpp
+++ b/src/router.cpp
@@ -162,7 +162,7 @@ int zmq::router_t::xsend (msg_t *msg_, int flags_)
             else 
             if (mandatory) {
                 more_out = false;
-                errno = EAGAIN;
+                errno = EHOSTUNREACH;
                 return -1;
             }
         }