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In 1998, Allan, Kakiko, OʼFarrell, and Watson proved a description of the closure (with respect to the uniform convergence of all derivatives on compact sets) of
A
(
ψ
)
=
{
F
∘
ψ
:
F
∈
E
(
R
d
)
}
for a smooth injective symbol
ψ
:
R
→
R
d
in terms of formal Taylor series. In that article it was conjectured that
A
(
ψ
)
is closed if
ψ is proper and has only critical points of finite order. In the present paper we first give a simple counterexample and then rectify the conjecture by adding a geometrical property for the curve
ψ
(
R
)
. This yields a characterization of
A
(
ψ
)
¯
=
A
(
ψ
)
.