diff --git a/jscomp/runtime/caml_int64.mli b/jscomp/runtime/caml_int64.mli
index a35e6c5a8e..e52616634b 100644
--- a/jscomp/runtime/caml_int64.mli
+++ b/jscomp/runtime/caml_int64.mli
@@ -28,7 +28,7 @@
 
 (** *)
 
-type t (* = { lo : nativeint; hi : nativeint; } *)
+type t 
 val min_int : t
 val max_int : t
 val one : t
@@ -77,7 +77,10 @@ val compare : t -> t -> int
 
 
 val float_of_bits : t -> float 
+
+(** [bits_of_float fl] it is undefined behaivor when [f] is NaN*)
 val bits_of_float : float -> t 
+
 val get64 : string -> int -> t
 
 
diff --git a/jscomp/stdlib-406/release.ninja b/jscomp/stdlib-406/release.ninja
index 961cf19c69..3a9f2455cd 100644
--- a/jscomp/stdlib-406/release.ninja
+++ b/jscomp/stdlib-406/release.ninja
@@ -62,7 +62,7 @@ build stdlib-406/gc.cmj : cc_cmi stdlib-406/gc.ml | stdlib-406/gc.cmi stdlib-406
 build stdlib-406/gc.cmi : cc stdlib-406/gc.mli | stdlib-406/pervasives.cmj others
 build stdlib-406/genlex.cmj : cc_cmi stdlib-406/genlex.ml | stdlib-406/bytes.cmj stdlib-406/char.cmj stdlib-406/genlex.cmi stdlib-406/hashtbl.cmj stdlib-406/list.cmj stdlib-406/stream.cmj stdlib-406/string.cmj others
 build stdlib-406/genlex.cmi : cc stdlib-406/genlex.mli | stdlib-406/pervasives.cmj stdlib-406/stream.cmi others
-build stdlib-406/hashtbl.cmj : cc_cmi stdlib-406/hashtbl.ml | stdlib-406/array.cmj stdlib-406/hashtbl.cmi stdlib-406/lazy.cmj stdlib-406/obj.cmj stdlib-406/random.cmj stdlib-406/string.cmj stdlib-406/sys.cmj others
+build stdlib-406/hashtbl.cmj : cc_cmi stdlib-406/hashtbl.ml | stdlib-406/array.cmj stdlib-406/hashtbl.cmi stdlib-406/lazy.cmj stdlib-406/random.cmj stdlib-406/string.cmj stdlib-406/sys.cmj others
 build stdlib-406/hashtbl.cmi : cc stdlib-406/hashtbl.mli | stdlib-406/pervasives.cmj others
 build stdlib-406/int32.cmj : cc_cmi stdlib-406/int32.ml | stdlib-406/int32.cmi stdlib-406/pervasives.cmj others
 build stdlib-406/int32.cmi : cc stdlib-406/int32.mli | stdlib-406/pervasives.cmj others
diff --git a/jscomp/test/int64_test.js b/jscomp/test/int64_test.js
index ab18da7bef..bf9f340ff8 100644
--- a/jscomp/test/int64_test.js
+++ b/jscomp/test/int64_test.js
@@ -2354,39 +2354,50 @@ function eq(loc, x, y) {
 }
 
 function id(loc, x) {
-  return eq(loc, Caml_int64.bits_of_float(Caml_int64.float_of_bits(x)), x);
+  var float_value = Caml_int64.float_of_bits(x);
+  var match = Pervasives.classify_float(float_value);
+  if (match >= 4) {
+    return /* () */0;
+  } else {
+    return eq(loc, Caml_int64.bits_of_float(float_value), x);
+  }
 }
 
-eq("File \"int64_test.ml\", line 176, characters 5-12", Caml_int64.bits_of_float(0.3), /* int64 */[
+eq("File \"int64_test.ml\", line 181, characters 5-12", Caml_int64.bits_of_float(0.3), /* int64 */[
       /* hi */1070805811,
       /* lo */858993459
     ]);
 
-eq("File \"int64_test.ml\", line 177, characters 5-12", Caml_int64.float_of_bits(/* int64 */[
+eq("File \"int64_test.ml\", line 182, characters 5-12", Caml_int64.float_of_bits(/* int64 */[
           /* hi */1070805811,
           /* lo */858993459
         ]), 0.3);
 
-id("File \"int64_test.ml\", line 178, characters 5-12", /* int64 */[
+id("File \"int64_test.ml\", line 183, characters 5-12", /* int64 */[
       /* hi */-1,
       /* lo */4294967295
     ]);
 
-id("File \"int64_test.ml\", line 179, characters 5-12", /* int64 */[
+id("File \"int64_test.ml\", line 184, characters 5-12", /* int64 */[
       /* hi */-1,
       /* lo */4294967196
     ]);
 
-id("File \"int64_test.ml\", line 180, characters 5-12", /* int64 */[
+id("File \"int64_test.ml\", line 185, characters 5-12", /* int64 */[
       /* hi */0,
       /* lo */4294967295
     ]);
 
-id("File \"int64_test.ml\", line 181, characters 5-12", /* int64 */[
+id("File \"int64_test.ml\", line 186, characters 5-12", /* int64 */[
       /* hi */0,
       /* lo */536870911
     ]);
 
+id("File \"int64_test.ml\", line 187, characters 5-12", /* int64 */[
+      /* hi */0,
+      /* lo */536870655
+    ]);
+
 Mt.from_pair_suites("Int64_test", suites$1[0]);
 
 exports.f = f;
diff --git a/jscomp/test/int64_test.ml b/jscomp/test/int64_test.ml
index 041bb10249..face420598 100644
--- a/jscomp/test/int64_test.ml
+++ b/jscomp/test/int64_test.ml
@@ -171,13 +171,19 @@ let test_id = ref 0
 let eq loc x y = Mt.eq_suites ~test_id ~suites loc x y 
 
 let id loc (x : int64) =  
-  eq loc (Int64.bits_of_float (Int64.float_of_bits x)) x 
+  (* This is not a round trip, since NaN is not distinguishable in JS*)
+  let float_value = (Int64.float_of_bits x) in 
+  match classify_float float_value  with
+  | FP_nan -> ()
+  | _  -> 
+     eq loc (Int64.bits_of_float float_value) x 
 let () = 
   eq __LOC__ (Int64.bits_of_float 0.3) 4599075939470750515L;
   eq __LOC__ (Int64.float_of_bits 4599075939470750515L) 0.3;
   id __LOC__ (-1L);
   id __LOC__ (-100L);
   id __LOC__ 0xff_ff_ff_ffL;
-  id __LOC__ 0x1f_ff_ff_ffL
+  id __LOC__ 0x1f_ff_ff_ffL;
+  id __LOC__ 0x1f_ff_fe_ffL
 
 ;; Mt.from_pair_suites __MODULE__ !suites
diff --git a/scripts/prebuilt.js b/scripts/prebuilt.js
index 87387b39db..35e7aa041b 100755
--- a/scripts/prebuilt.js
+++ b/scripts/prebuilt.js
@@ -1,3 +1,4 @@
+#!/usr/bin/env node
 //@ts-check
 var cp = require("child_process");
 var path = require("path");