diff --git a/include/zmq.h b/include/zmq.h
index 154a78ca..53e63682 100644
--- a/include/zmq.h
+++ b/include/zmq.h
@@ -204,7 +204,7 @@ ZMQ_EXPORT int zmq_ctx_destroy (void *context);
 /*  0MQ message definition.                                                   */
 /******************************************************************************/
 
-typedef struct zmq_msg_t {unsigned char _ [48];} zmq_msg_t;
+typedef struct zmq_msg_t {unsigned char _ [64];} zmq_msg_t;
 
 typedef void (zmq_free_fn) (void *data, void *hint);
 
diff --git a/src/msg.hpp b/src/msg.hpp
index ea2bb4e4..04eb8f63 100644
--- a/src/msg.hpp
+++ b/src/msg.hpp
@@ -92,7 +92,7 @@ namespace zmq
 
         //  Size in bytes of the largest message that is still copied around
         //  rather than being reference-counted.
-        enum { msg_t_size = 48 };
+        enum { msg_t_size = 64 };
         enum { max_vsm_size = msg_t_size - (8 + sizeof (metadata_t *) + 3) };
 
         //  Shared message buffer. Message data are either allocated in one