diff --git a/prometheuspvesd/config.py b/prometheuspvesd/config.py
index 9bf3c47..84185ea 100644
--- a/prometheuspvesd/config.py
+++ b/prometheuspvesd/config.py
@@ -285,11 +285,8 @@ class Config:
         try:
             anyconfig.validate(config, self.schema, ac_schema_safe=False)
         except jsonschema.exceptions.ValidationError as e:
-            schema_error = "Failed validating '{validator}' in schema{schema}\n{message}".format(
-                validator=e.validator,
-                schema=format_as_index(list(e.relative_schema_path)[:-1], 0),
-                message=e.message,
-            )
+            schema = format_as_index(list(e.relative_schema_path)[:-1], 0)
+            schema_error = f"Failed validating '{e.validator}' in schema {schema}\n{e.message}"
             raise prometheuspvesd.exception.ConfigError("Configuration error", schema_error) from e
 
         return True