diff --git a/server/mapping.c b/server/mapping.c
index f9f50edfa60..d9bff4b2ead 100644
--- a/server/mapping.c
+++ b/server/mapping.c
@@ -507,13 +507,13 @@ static int build_shared_mapping( struct mapping *mapping, int fd,
         }
         if (pwrite( shared_fd, buffer, file_size, write_pos ) != file_size) goto error;
     }
-    free( buffer );
 
     if (!(shared = alloc_object( &shared_map_ops ))) goto error;
     shared->fd = (struct fd *)grab_object( mapping->fd );
     shared->file = file;
     list_add_head( &shared_map_list, &shared->entry );
     mapping->shared = shared;
+    free( buffer );
     return 1;
 
  error: