diff --git a/src/lustre/lustreSyntaxChecks.ml b/src/lustre/lustreSyntaxChecks.ml
index 27c1e416b..0025650cd 100644
--- a/src/lustre/lustreSyntaxChecks.ml
+++ b/src/lustre/lustreSyntaxChecks.ml
@@ -832,10 +832,12 @@ and check_expr ctx f (expr:LustreAst.expr) =
       (check_expr ctx f e1) >> (check_expr ctx f e2) >> (check_expr_list ctx f e3)
     | RestartEvery (_, _, e1, e2)
       -> (check_expr_list ctx f e1) >> (check_expr ctx f e2)
-    | ChooseOp (_, _, e1, None) -> 
-      (check_expr ctx f e1)
-    | ChooseOp (_, _, e1, Some e2) -> 
-      (check_expr ctx f e1) >> (check_expr ctx f e2)
+    | ChooseOp (_, (_, i, ty), e1, None) -> 
+      let extn_ctx = ctx_add_local ctx i (Some ty) in
+      (check_expr extn_ctx f e1)
+    | ChooseOp (_, (_, i, ty), e1, Some e2) -> 
+      let extn_ctx = ctx_add_local ctx i (Some ty) in
+      (check_expr extn_ctx f e1) >> (check_expr extn_ctx f e2)
     | _ -> Ok ()
   in
   expr' >> r