Fix failure in legacy opmath

[astralcai]

A follow up PR to #6278, fixes recent failure in legacy opmath.

[github-actions]

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Please edit doc/releases/changelog-dev.md with:

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[dwierichs]

LGTM 🎉
Do we track bugfixes for legacy op math in the changelog? :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.70%. Comparing base (be676fe) to head (7589d72).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6310   +/-   ##
=======================================
  Coverage   99.70%   99.70%           
=======================================
  Files         444      444           
  Lines       42223    42226    +3     
=======================================
+ Hits        42100    42103    +3     
  Misses        123      123           

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[astralcai]

LGTM 🎉 Do we track bugfixes for legacy op math in the changelog? :)

I'll update the changelog.