diff --git a/pybamm/meshes/scikit_fem_submeshes.py b/pybamm/meshes/scikit_fem_submeshes.py
index 604d058cbd..bfb76ef9d2 100644
--- a/pybamm/meshes/scikit_fem_submeshes.py
+++ b/pybamm/meshes/scikit_fem_submeshes.py
@@ -217,7 +217,7 @@ def __init__(self, lims, npts, tabs, side="top", stretch=2.3):
         # check side is top
         if side != "top":
             raise pybamm.GeometryError(
-                "At present, side can only be 'top', but is set to ".format(side)
+                "At present, side can only be 'top', but is set to {}".format(side)
             )
 
         # check that two variables have been passed in