diff --git a/src/submission.jl b/src/submission.jl
index f6b2090b9..ff2746a8e 100644
--- a/src/submission.jl
+++ b/src/submission.jl
@@ -220,7 +220,7 @@ end
 function EagerThunkMetadata(spec::EagerTaskSpec)
     f = chunktype(spec.f).instance
     arg_types = ntuple(i->chunktype(spec.args[i][2]), length(spec.args))
-    return_type = Base._return_type(f, Base.to_tuple_type(arg_types))
+    return_type = Base.promote_op(f, arg_types...)
     return EagerThunkMetadata(return_type)
 end
 chunktype(t::EagerThunk) = t.metadata.return_type