diff --git a/guppylang/prelude/quantum.py b/guppylang/prelude/quantum.py
index c87fe222..0d0db1f4 100644
--- a/guppylang/prelude/quantum.py
+++ b/guppylang/prelude/quantum.py
@@ -66,7 +66,7 @@ def sdg(q: qubit) -> qubit: ...
 
 
 @guppy.hugr_op(quantum, quantum_op("ZZMax"))
-def zz_max(q: qubit) -> qubit: ...
+def zz_max(q1: qubit, q2: qubit) -> tuple[qubit, qubit]: ...
 
 
 @guppy.hugr_op(quantum, quantum_op("Measure"))