diff --git a/src/control.c b/src/control.c
index 4c1c899..63f0720 100644
--- a/src/control.c
+++ b/src/control.c
@@ -569,7 +569,6 @@ void control_client_cleanup(struct control_client* client,
 	if (client->socket) { close(client->socket); }
 
 	/* This is wrongness */
-	if ( server_io_locked( client->flexnbd->serve ) ) { server_unlock_io( client->flexnbd->serve ); }
 	if ( server_acl_locked( client->flexnbd->serve ) ) { server_unlock_acl( client->flexnbd->serve ); }
 
 	control_client_destroy( client );
diff --git a/src/mirror.c b/src/mirror.c
index 30007a2..376b036 100644
--- a/src/mirror.c
+++ b/src/mirror.c
@@ -231,8 +231,9 @@ static const int mirror_maximum_passes = 7;
 
 /* This must not be called if there's any chance of further I/O. Methods to
  * ensure this include:
- *   - call server_lock_io()
- *   - call server_forbid_new_clients() followed by a successful server_close_clients() ; server_join_clients()
+ *   - Ensure image size is 0
+ *   - call server_forbid_new_clients() followed by a successful
+ *     server_close_clients() ; server_join_clients()
  */
 void mirror_on_exit( struct server * serve )
 {
@@ -281,8 +282,6 @@ void mirror_cleanup( struct server * serve,
 		close( mirror->client );
 	}
 	mirror->client = -1;
-
-	if( server_io_locked( serve ) ){ server_unlock_io( serve ); }
 }
 
 
diff --git a/src/serve.c b/src/serve.c
index 4c9d8ee..348aeda 100644
--- a/src/serve.c
+++ b/src/serve.c
@@ -69,8 +69,7 @@ struct server * server_create (
 	strcpy(out->filename_incomplete, s_file);
 	strcpy(out->filename_incomplete + strlen(s_file), ".INCOMPLETE");
 
-	out->l_io = flexthread_mutex_create();
-	out->l_acl= flexthread_mutex_create();
+	out->l_acl = flexthread_mutex_create();
 	out->l_start_mirror = flexthread_mutex_create();
 
 	out->mirror_can_start = 1;
@@ -93,7 +92,6 @@ void server_destroy( struct server * serve )
 
 	flexthread_mutex_destroy( serve->l_start_mirror );
 	flexthread_mutex_destroy( serve->l_acl );
-	flexthread_mutex_destroy( serve->l_io );
 
 	if ( serve->acl ) {
 		acl_destroy( serve->acl );
@@ -126,30 +124,6 @@ void server_unlink( struct server * serve )
 	do { NULLCHECK( s ); \
 	 FATAL_IF( 0 != flexthread_mutex_unlock( s->f ), msg ); } while (0)
 
-void server_lock_io( struct server * serve)
-{
-	debug("IO locking");
-
-	SERVER_LOCK( serve, l_io, "Problem with I/O lock" );
-}
-
-void server_unlock_io( struct server* serve )
-{
-	debug("IO unlocking");
-
-	SERVER_UNLOCK( serve, l_io, "Problem with I/O unlock" );
-}
-
-
-/* This is only to be called from error handlers. */
-int server_io_locked( struct server * serve )
-{
-	NULLCHECK( serve );
-	return flexthread_mutex_held( serve->l_io );
-}
-
-
-
 void server_lock_acl( struct server *serve )
 {
 	debug("ACL locking");
diff --git a/src/serve.h b/src/serve.h
index a532679..256bc3b 100644
--- a/src/serve.h
+++ b/src/serve.h
@@ -38,9 +38,6 @@ struct server {
 	/** size of file */
 	uint64_t 	     size;
 
-	/** Claims around any I/O to this file */
-	struct flexthread_mutex * l_io;
-
 	/** to interrupt accept loop and clients, write() to close_signal[1] */
 	struct self_pipe *   close_signal;
 
@@ -93,7 +90,6 @@ struct server {
 	/** If this isn't set, newly accepted clients will be closed immediately */
 	int allow_new_clients;
 
-
 	/* Marker for whether this server has control over the data in
 	 * the file, or if we're waiting to receive it from an inbound
 	 * migration which hasn't yet finished.
@@ -117,15 +113,12 @@ struct server * server_create(
 		int success );
 void server_destroy( struct server * );
 int server_is_closed(struct server* serve);
-void server_lock_io( struct server * serve);
-void server_unlock_io( struct server* serve );
 void serve_signal_close( struct server *serve );
 void serve_wait_for_close( struct server * serve );
 void server_replace_acl( struct server *serve, struct acl * acl);
 void server_control_arrived( struct server *serve );
 int server_is_in_control( struct server *serve );
 int server_default_deny( struct server * serve );
-int server_io_locked( struct server * serve );
 int server_acl_locked( struct server * serve );
 void server_lock_acl( struct server *serve );
 void server_unlock_acl( struct server *serve );