diff --git a/fairmq/shmem/Socket.h b/fairmq/shmem/Socket.h
index ae8d7f53..1919db1b 100644
--- a/fairmq/shmem/Socket.h
+++ b/fairmq/shmem/Socket.h
@@ -505,6 +505,8 @@ class Socket final : public fair::mq::Socket
         if (constant == "no-block") return ZMQ_DONTWAIT;
         if (constant == "snd-more no-block") return ZMQ_DONTWAIT|ZMQ_SNDMORE;
 
+        if (constant == "fd") return ZMQ_FD;
+
         return -1;
     }
 
diff --git a/fairmq/zeromq/Socket.h b/fairmq/zeromq/Socket.h
index ecd129f0..ca2454c2 100644
--- a/fairmq/zeromq/Socket.h
+++ b/fairmq/zeromq/Socket.h
@@ -459,6 +459,8 @@ class Socket final : public fair::mq::Socket
 
         if (constant == "linger") return ZMQ_LINGER;
 
+        if (constant == "fd") return ZMQ_FD;
+
         return -1;
     }