Index: uspace/lib/libblock/libblock.c
===================================================================
--- uspace/lib/libblock/libblock.c	(revision 62140db53b75a953d42ed31acb77916cfc0ee678)
+++ uspace/lib/libblock/libblock.c	(revision 61d23157851792db1cc8126e35bfe4099ee1779b)
@@ -394,6 +394,8 @@
 			 * the new contents from the device.
 			 */
+			async_serialize_start();
 			rc = block_read(dev_handle, &bufpos, &buflen, &pos,
 			    b->data, cache->block_size, cache->block_size);
+			async_serialize_end();
 			assert(rc == EOK);
 		}