ocamlbuild_failing

$ ocamlbuild -use-ocamlfind -pkgs cohttp.lwt,aws,aws.lwt,aws_ec2 -cflag -g -lflags -g,-linkpkg -I src/ main.native
+ ocamlfind ocamlopt -g -linkpkg -linkpkg -package aws_ec2 -package aws.lwt -package aws -package cohttp.lwt src/main.cmx -o src/main.native
File "_none_", line 1:
Error: No implementations provided for the following modules:
         Cohttp_lwt_unix referenced from /Users/s/.opam/4.02.3/lib/aws/aws_lwt.cmxa(Aws_lwt)
Command exited with code 2.
Hint: Recursive traversal of subdirectories was not enabled for this build,
  as the working directory does not look like an ocamlbuild project (no
  '_tags' or 'myocamlbuild.ml' file). If you have modules in subdirectories,
  you should add the option "-r" or create an empty '_tags' file.

  To enable recursive traversal for some subdirectories only, you can use the
  following '_tags' file:

      true: -traverse
      <dir1> or <dir2>: traverse

Compilation unsuccessful after building 4 targets (0 cached) in 00:00:00.