diff --git a/mbtrack2/impedance/impedance_model.py b/mbtrack2/impedance/impedance_model.py
index bc3da3c0f8f7b3bb2794e580668c1efdc1783239..cf586387aea1e5dd7d78f23ee23ec373df9eab9a 100644
--- a/mbtrack2/impedance/impedance_model.py
+++ b/mbtrack2/impedance/impedance_model.py
@@ -102,8 +102,6 @@ class ImpedanceModel():
         None.
 
         """
-        self.wakefields.append(wakefield)
-        self.positions.append(positions)
         if name is None:
             name = wakefield.name
         if name is None:
@@ -112,6 +110,8 @@ class ImpedanceModel():
             self.names.append(name)
         else:
             raise ValueError("This name is already taken.")
+        self.wakefields.append(wakefield)
+        self.positions.append(positions)
 
     def add_global(self, wakefield, name=None):
         """
diff --git a/mbtrack2/tracking/wakepotential.py b/mbtrack2/tracking/wakepotential.py
index 43a16927e20fa96553d9b503522ceced5fe74200..19bee813701ab7a7d27299a7f271e2ad23c99f3b 100644
--- a/mbtrack2/tracking/wakepotential.py
+++ b/mbtrack2/tracking/wakepotential.py
@@ -793,7 +793,7 @@ class LongRangeResistiveWall(Element):
         for wake_type in self.types:
             kick = self.get_kick(rank, wake_type)
             if wake_type == "Wlong":
-                bunch["delta"] += kick / self.ring.E0
+                bunch["delta"] -= kick / self.ring.E0
             elif wake_type == "Wxdip":
                 bunch["xp"] += kick / self.ring.E0
             elif wake_type == "Wydip":