diff --git a/tracking/wakepotential.py b/tracking/wakepotential.py
index 223dd433136f4276aa45907e619ece36bcf8bc77..9741ef5b2a368248be7db54cd9e27b8ea9664150 100644
--- a/tracking/wakepotential.py
+++ b/tracking/wakepotential.py
@@ -619,7 +619,10 @@ class LongRangeResistiveWall(Element):
         self.rho = rho
         self.nt = int(nt)
         self.nb = len(beam)
-        self.types = types
+        if isinstance(types, str):
+            self.types = [types]
+        elif isinstance(types, list):
+            self.types = types
         
         # effective radius for RW
         self.radius = radius