diff --git a/guppylang/tys/ty.py b/guppylang/tys/ty.py
index ff1991b3..ee876a9d 100644
--- a/guppylang/tys/ty.py
+++ b/guppylang/tys/ty.py
@@ -226,7 +226,7 @@ def transform(self, transformer: Transformer) -> "Type":
 
 @dataclass(frozen=True)
 class NoneType(TypeBase):
-    """Type of tuples."""
+    """Type of `None`."""
 
     linear: bool = field(default=False, init=False)
     hugr_bound: ht.TypeBound = field(default=ht.TypeBound.Copyable, init=False)