  Let $(s_2(n))_{n\in \mathbb{N}}$ be a $0,1$-sequence such that, for any
natural number $n$, $s_2(n) = 1$ if and only if $n$ is a sum of two squares. In
a recent article, Tahay proved that the sequence $(s_2(n))_{n\in \mathbb{N}}$
is not $k$-automatic for any integer $k$, and asked if this sequence can be
morphic. In this note, we give a negative answer to this question.
