diff --git a/mysys/mf_iocache.c b/mysys/mf_iocache.c
index d861c2c3d4f..a0ddc3e40a5 100644
--- a/mysys/mf_iocache.c
+++ b/mysys/mf_iocache.c
@@ -300,7 +300,7 @@ int init_io_cache(IO_CACHE *info, File file, size_t cachesize,
   else
   {
     /* Clear mutex so that safe_mutex will notice that it's not initialized */
-    bzero((char*) &info->append_buffer_lock, sizeof(info));
+    bzero((char*) &info->append_buffer_lock, sizeof(info->append_buffer_lock));
   }
 #endif
 
diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index e1d22e6a1e9..db9f9013188 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -701,6 +701,8 @@ int mysql_update(THD *thd,
       if (reinit_io_cache(&tempfile,READ_CACHE,0L,0,0))
 	error=1; /* purecov: inspected */
       select->file=tempfile;			// Read row ptrs from this file
+      // select->file was copied, update self-references.
+      setup_io_cache(&select->file);
       if (error >= 0)
 	goto err;
     }