diff --git a/linkml_model/model/schema/extended_types.yaml b/linkml_model/model/schema/extended_types.yaml
index c709f627..0298fc62 100644
--- a/linkml_model/model/schema/extended_types.yaml
+++ b/linkml_model/model/schema/extended_types.yaml
@@ -145,9 +145,8 @@ types:
 
   float64:
     aliases:
-    - d
+      - d
     typeof: float
     description: A 64-bit floating point number
     see_also:
       - https://numpy.org/doc/stable/reference/arrays.scalars.html#numpy.float64
-