diff --git a/model-single-origin-samples/biokepi/run_execute_ipynb.ml b/model-single-origin-samples/biokepi/run_execute_ipynb.ml
index c9643f9..46838f0 100644
--- a/model-single-origin-samples/biokepi/run_execute_ipynb.ml
+++ b/model-single-origin-samples/biokepi/run_execute_ipynb.ml
@@ -76,7 +76,7 @@ let my_notebook =
 
 let timeout =
   let doc="The maximum time (in seconds) each notebook cell is allowed to run. If the execution takes longer an exception will be raised. Can set to -1 for no maximum timeout." in
-  Arg.(value & opt int -1 & info ["t"; "timeout"] ~docv:"TIMEOUT_SECS" ~doc)
+  Arg.(value & opt int (-1) & info ["t"; "timeout"] ~docv:"TIMEOUT_SECS" ~doc)
 
 let cmd =
   let doc = "Execute jupyter notebook. Saves to {mynotebook}.nbconvert.ipynb" in