diff --git a/math/mkessler-mathop.sty b/math/mkessler-mathop.sty
index f0d4b30..c3ac6e9 100644
--- a/math/mkessler-mathop.sty
+++ b/math/mkessler-mathop.sty
@@ -175,3 +175,5 @@
 \DeclarePairedDelimiter\norm{\lVert}{\rVert}
 \let\oldnorm\norm
 \def\norm{\@ifstar{\oldnorm}{\oldnorm*}}
+
+\DeclareMathOperator{\amalgprod}{\star}