diff --git a/src/rt/rustrt.def.in b/src/rt/rustrt.def.in
index dc94c73d813d..5abd928140f0 100644
--- a/src/rt/rustrt.def.in
+++ b/src/rt/rustrt.def.in
@@ -50,6 +50,7 @@ str_vec
 task_sleep
 task_yield
 task_join
+task_unsupervise
 unsafe_vec_to_mut
 unsupervise
 upcall_clone_chan