--- a/src/core/dune
+++ b/src/core/dune
@@ -7,6 +7,6 @@
  (preprocess (action (run %{project_root}/src/core/cpp/cpp.exe %{input-file})))
  (flags :standard -warn-error -a+8 -w -32-70 -safe-string
         -strict-sequence -nolabels -open CCMonomorphic)
- (libraries seq either containers.monomorphic))
+ (libraries containers.monomorphic))
 
 (ocamllex (modules CCSexp_lex))