diff --git a/evrouting/charge/T.py b/evrouting/charge/T.py
index 259aa4bc989135ed9375e5a1ee91aae1aad9cbb6..d65d7bc64cdd9d3b087d52d42b422d002b42acd9 100644
--- a/evrouting/charge/T.py
+++ b/evrouting/charge/T.py
@@ -13,8 +13,8 @@ Label = namedtuple('Label', ['t_trip', 'beta_u', 'u', 'SoCProfile_u_v'])
 class ChargingFunction:
 
     def __init__(self, G: nx.Graph, n: Node, U: SoC):
-        self.c = charging_cofficient(G, n)
-        self.U = U
+        self.c: ChargingCoefficient = charging_cofficient(G, n)
+        self.U: SoC = U
 
     def __call__(self, t: Time, beta: SoC = 0) -> SoC:
         beta += self.c * t