diff --git a/src/math/mathop.pysty b/src/math/mathop.pysty
index bb57ed0..0c5c3b1 100644
--- a/src/math/mathop.pysty
+++ b/src/math/mathop.pysty
@@ -79,6 +79,7 @@ __END_OPTIONS_X__
 \DeclareSimpleMathOperator{rank}
 \DeclareSimpleMathOperator{Mat}
 \DeclareSimpleMathOperator{ev}
+\DeclareSimpleMathOperator{tr}
 
 %Algebra
 \DeclareSimpleMathOperator{Quot}