diff --git a/src/proto/genesis/data.ml b/src/proto/genesis/data.ml
index 14efcb482..78d7c9a77 100644
--- a/src/proto/genesis/data.ml
+++ b/src/proto/genesis/data.ml
@@ -93,9 +93,7 @@ end
 
 module Init = struct
 
-  type error +=
-  | Incompatible_protocol_version
-  | Decreasing_fitness
+  type error += Incompatible_protocol_version
 
   let version_key = ["version"]