diff --git a/telethon_generator/parsers/errors.py b/telethon_generator/parsers/errors.py
index 869ca96e..03c42a6d 100644
--- a/telethon_generator/parsers/errors.py
+++ b/telethon_generator/parsers/errors.py
@@ -46,8 +46,8 @@ def _get_class_name(error_code):
             error_code, 'RPCError' + str(error_code).replace('-', 'Neg')
         )
 
-    return snake_to_camel_case(error_code.replace('FIRSTNAME', 'FIRST_NAME'),
-                               suffix='Error')
+    return snake_to_camel_case(
+        error_code.replace('FIRSTNAME', 'FIRST_NAME').lower(), suffix='Error')
 
 
 class Error:
diff --git a/telethon_generator/utils.py b/telethon_generator/utils.py
index c28c27b4..9889803f 100644
--- a/telethon_generator/utils.py
+++ b/telethon_generator/utils.py
@@ -3,6 +3,6 @@ import re
 
 def snake_to_camel_case(name, suffix=None):
     # Courtesy of http://stackoverflow.com/a/31531797/4759433
-    result = re.sub(r'_([a-z])', lambda m: m.group(1).upper(), name.lower())
+    result = re.sub(r'_([a-z])', lambda m: m.group(1).upper(), name)
     result = result[:1].upper() + result[1:].replace('_', '')
     return result + suffix if suffix else result