diff --git a/dune-project b/dune-project
index 5a2aac5..99e7a26 100644
--- a/dune-project
+++ b/dune-project
@@ -6,6 +6,8 @@
 
 (generate_opam_files true)
 
+(use_standard_c_and_cxx_flags true)
+
 (source
  (github anmonteiro/piaf))
 
diff --git a/lib/cflags/cflags.ml b/lib/cflags/cflags.ml
new file mode 100644
index 0000000..a8b691c
--- /dev/null
+++ b/lib/cflags/cflags.ml
@@ -0,0 +1,29 @@
+module C = Configurator.V1
+
+let directory_exists fsp = Sys.file_exists fsp && Sys.is_directory fsp
+
+let default c : C.Pkg_config.package_conf =
+  if C.ocaml_config_var_exn c "system" = "macosx"
+  then
+    if directory_exists "/usr/local/opt/openssl"
+    then
+      { libs = [ "-L/usr/local/opt/openssl/lib" ]
+      ; cflags = [ "-I/usr/local/opt/openssl/include" ]
+      }
+    else { libs = [ "-L/opt/local/lib" ]; cflags = [ "-I/opt/local/include" ] }
+  else { libs = [ "-lssl"; "-lcrypto" ]; cflags = [] }
+
+let () =
+  C.main ~name:"ssl" (fun c ->
+      let default = default c in
+      let conf =
+        match C.Pkg_config.get c with
+        | None -> default
+        | Some pc ->
+          (match C.Pkg_config.query pc ~package:"openssl" with
+          | Some s -> s
+          | None -> default)
+      in
+      C.Flags.write_sexp "c_library_flags.sexp" conf.libs;
+      C.Flags.write_sexp "c_flags.sexp" conf.cflags)
+
diff --git a/lib/cflags/dune b/lib/cflags/dune
new file mode 100644
index 0000000..d73d966
--- /dev/null
+++ b/lib/cflags/dune
@@ -0,0 +1,4 @@
+(executable
+ (name cflags)
+ (libraries dune-configurator))
+
diff --git a/lib/dune b/lib/dune
index 8f547d5..094f20c 100644
--- a/lib/dune
+++ b/lib/dune
@@ -21,4 +21,13 @@
   piaf.stream)
  (foreign_stubs
   (language c)
-  (names piaf_bigarray_read piaf_openssl_rand piaf_openssl_sha piaf_fdutils)))
+  (names piaf_bigarray_read piaf_openssl_rand piaf_openssl_sha piaf_fdutils)
+  (flags (:include c_flags.sexp)))
+ (c_library_flags
+  (:include c_library_flags.sexp)))
+
+(rule
+ (targets c_flags.sexp c_library_flags.sexp)
+ (action
+  (run ./cflags/cflags.exe)))
+