diff --git a/src/copapy/_autograd.py b/src/copapy/_autograd.py
index 2413da2..623879c 100644
--- a/src/copapy/_autograd.py
+++ b/src/copapy/_autograd.py
@@ -31,6 +31,8 @@ def grad(x: Any, y: value[Any] | Sequence[value[Any]] | vector[Any] | tensor[Any
     """
     assert isinstance(x, value), f"Argument x for grad function must be a copapy value but is {type(x)}."
 
+    y_set: set[value[float] | float]
+
     if isinstance(y, value):
         y_set = {y}
     if isinstance(y, tensor):
diff --git a/src/copapy/_quaternion.py b/src/copapy/_quaternion.py
index b1445dc..f9b3dfe 100644
--- a/src/copapy/_quaternion.py
+++ b/src/copapy/_quaternion.py
@@ -218,7 +218,7 @@ class quaternion(ArrayType[float]):
         return self.norm()
 
     def __repr__(self) -> str:
-        return f"vector({self.values})"
+        return f"quaternion(w={self.w}, x={self.x}, y={self.y}, z={self.z})"
 
     def __len__(self) -> int:
         return len(self.values)