diff --git a/src/interpretation.ml b/src/interpretation.ml
index aa2b97ff3bd22e629bf5cdb9576d972664fa88d4..b0a68d578b6755b7bf6494dab693d91bba0e6012 100644
--- a/src/interpretation.ml
+++ b/src/interpretation.ml
@@ -44,18 +44,13 @@ type dataset = DS_csv of Csv.t [@printer fun fmt _ -> Fmt.pf fmt "<csv>"]
 
 type data = D_csv of string list [@@deriving show]
 
-type vector =
-  (Term.lsymbol
-  [@printer
-    fun fmt v ->
-      Fmt.pf fmt "%a" Fmt.(option ~none:nop int) (Language.lookup_vector v)])
-[@@deriving show]
-
 type caisar_op =
   | NeuralNetwork of nn
   | Dataset of dataset
   | Data of data
-  | Vector of vector
+  | Vector of Term.lsymbol
+      [@printer
+        fun fmt v -> Fmt.pf fmt "%a" Fmt.(option int) (Language.lookup_vector v)]
 [@@deriving show]
 
 type caisar_env = {