diff --git a/jscomp/ext_pervasives.ml b/jscomp/ext_pervasives.ml
index f427756f2e..614d86dedb 100644
--- a/jscomp/ext_pervasives.ml
+++ b/jscomp/ext_pervasives.ml
@@ -18,13 +18,13 @@
 
 (* Author: Hongbo Zhang  *)
 
-
+external reraise: exn -> 'a = "%reraise"
 
 let finally v f  action = 
   match f v with
   | exception e -> 
       action v ;
-      raise e 
+      reraise e 
   | e ->  action v ; e 
 
 let with_file_as_chan filename f = 
diff --git a/jscomp/ext_pervasives.mli b/jscomp/ext_pervasives.mli
index c8ee85baae..caa12396bb 100644
--- a/jscomp/ext_pervasives.mli
+++ b/jscomp/ext_pervasives.mli
@@ -23,6 +23,7 @@
 (** Extension to standard library [Pervavives] module, safe to open 
   *)
 
+external reraise: exn -> 'a = "%reraise"
 val finally : 'a -> ('a -> 'b) -> ('a -> 'c) -> 'b
 
 val with_file_as_chan : string -> (out_channel -> 'a) -> 'a
diff --git a/jscomp/js_implementation.ml b/jscomp/js_implementation.ml
index 77e845198b..7091e334f2 100644
--- a/jscomp/js_implementation.ml
+++ b/jscomp/js_implementation.ml
@@ -49,9 +49,20 @@ let implementation ppf sourcefile outputprefix =
       |> Translmod.transl_implementation modulename
       |> print_if ppf Clflags.dump_rawlambda Printlambda.lambda
       |> (fun lambda -> 
-          Lam_compile_group.lambda_as_module true
+          match           
+          Lam_compile_group.lambda_as_module
             finalenv current_signature 
-            sourcefile  lambda);
+            sourcefile  lambda with
+          | e -> e 
+          | exception e -> 
+            (* Save to a file instead so that it will not scare user *)            
+            let file = "osc.dump" in
+            Ext_pervasives.with_file_as_chan file
+              (fun ch -> output_string ch @@             
+                Printexc.raw_backtrace_to_string (Printexc.get_raw_backtrace ()));
+            Ext_log.err __LOC__ "Compilation fatal error, stacktrace saved into %s" file ;             
+            raise e             
+        );
     end;
     Stypes.dump (Some (outputprefix ^ ".annot"));
   with x ->
diff --git a/jscomp/js_pass_flatten_and_mark_dead.ml b/jscomp/js_pass_flatten_and_mark_dead.ml
index e0b9cc2cc4..a7bae8c6c8 100644
--- a/jscomp/js_pass_flatten_and_mark_dead.ml
+++ b/jscomp/js_pass_flatten_and_mark_dead.ml
@@ -143,8 +143,16 @@ let mark_dead_code js =
 
    Take away, it is really hard to change the code while collecting some information..
    we should always collect info in a single pass
+
+   Note that, we should avoid reuse object, i.e,
+   {[
+     let v = 
+       object 
+       end      
+   ]}   
+   Since user may use `osc -c xx.ml xy.ml xz.ml` and we need clean up state
  *)
-let subst_map = object (self)
+let subst_map name = object (self)
   inherit Js_map.map as super
 
   val mutable substitution = Hashtbl.create 17 
@@ -213,9 +221,19 @@ let subst_map = object (self)
       begin match Hashtbl.find self#get_substitution id with 
         | {expression_desc = Array (ls, Immutable) } 
           -> 
+          (* user program can be wrong, we should not 
+             turn a runtime crash into compile time crash : )
+          *)          
           begin match List.nth ls i with 
             | {expression_desc = J.Var _ | Number _ | Str _ } as x 
               -> x 
+            | exception _ ->
+              begin
+                Ext_log.err __LOC__ "suspcious code %s when compiling %s@."
+                  (Printf.sprintf "%s/%d" id.name id.stamp)
+                  name  ;
+                super#expression x ;
+              end
             | _ -> 
               (** we can do here, however, we should 
                   be careful that it can only be done 
@@ -266,9 +284,9 @@ end
     there is no need to add another pass
  *)
 
-let program  js = 
+let program  (js : J.program) = 
   js 
-  |> subst_map#program
+  |> (subst_map js.name )#program
   |> mark_dead_code
   (* |> mark_dead_code *)
   (* mark dead code twice does have effect in some cases, however, we disabled it 
diff --git a/jscomp/lam_compile_group.ml b/jscomp/lam_compile_group.ml
index 2507a1d415..f7cdf87bff 100644
--- a/jscomp/lam_compile_group.ml
+++ b/jscomp/lam_compile_group.ml
@@ -297,7 +297,6 @@ let compile ~filename env sigs lam  : J.program  =
 let current_file_name : string option ref  = ref None;;
 
 let lambda_as_module 
-    (raw : bool) 
     env 
     (sigs : Types.signature)
     (filename : string) 
diff --git a/jscomp/lam_compile_group.mli b/jscomp/lam_compile_group.mli
index 8798c0e377..4fa161b3c0 100644
--- a/jscomp/lam_compile_group.mli
+++ b/jscomp/lam_compile_group.mli
@@ -35,4 +35,4 @@ val compile :
   Lambda.lambda -> 
   J.program
 
-val lambda_as_module : bool -> Env.t -> Types.signature -> string -> Lambda.lambda -> unit
+val lambda_as_module :  Env.t -> Types.signature -> string -> Lambda.lambda -> unit
diff --git a/jscomp/lam_register.ml b/jscomp/lam_register.ml
index 562a28340b..dccff9cf9b 100644
--- a/jscomp/lam_register.ml
+++ b/jscomp/lam_register.ml
@@ -1,3 +1,3 @@
 let () = 
-  Printlambda.serialize_raw_js := Lam_compile_group.lambda_as_module true;
+  Printlambda.serialize_raw_js := Lam_compile_group.lambda_as_module;
 ;;
diff --git a/jscomp/lam_register.mli b/jscomp/lam_register.mli
new file mode 100644
index 0000000000..43bee504f9
--- /dev/null
+++ b/jscomp/lam_register.mli
@@ -0,0 +1 @@
+(** *)