  This paper presents a novel proof of the conservativity of the intuitionistic
theory of strictly positive fixpoints,
$\widehat{\mathrm{ID}}{}_{1}^{\mathrm{i}}$, over Heyting arithmetic (HA),
originally proved in full generality by Arai (2011). The proof embeds
$\widehat{\mathrm{ID}}{}_{1}^{\mathrm{i}}$ into the corresponding theory over
Beeson's logic of partial terms and then uses two consecutive interpretations,
a realizability interpretation of this theory into the subtheory generated by
almost negative fixpoints, and a direct interpretation into Heyting arithmetic
with partial terms using a hierarchy of satisfaction predicates for almost
negative formulae. It concludes by applying van den Berg and van Slooten's
result (2018) that Heyting arithmetic with partial terms plus the schema of
self realizability for arithmetic formulae is conservative over HA.
