diff --git a/pywatershed/utils/netcdf_utils.py b/pywatershed/utils/netcdf_utils.py
index 1b70515f..4740d74c 100644
--- a/pywatershed/utils/netcdf_utils.py
+++ b/pywatershed/utils/netcdf_utils.py
@@ -533,7 +533,7 @@ def __init__(
                     # S1 gives "char" type in the file whereas another
                     # number gives "string" type. The former is properly
                     # handled by xarray
-                    nc_type = f"S1"
+                    nc_type = "S1"
                     if nc_type in dims_created:
                         continue