diff --git a/Lib/fontTools/designspaceLib/types.py b/Lib/fontTools/designspaceLib/types.py
index 9279e3f71..8afea96c9 100644
--- a/Lib/fontTools/designspaceLib/types.py
+++ b/Lib/fontTools/designspaceLib/types.py
@@ -24,7 +24,7 @@ class Range:
     default: float = 0
     """Default value"""
 
-    def __post__init__(self):
+    def __post_init__(self):
         self.minimum, self.maximum = sorted((self.minimum, self.maximum))
         self.default = clamp(self.default, self.minimum, self.maximum)