Module.ccall also does not work in asm.js

asmjs-test.c

#include <stdio.h>

#include <emscripten/emscripten.h>

int EMSCRIPTEN_KEEPALIVE c_func_calling_from_js() {
  printf("This is a c function calling from js!");

  return 0;
}

extern void js_func();

int main(int argc, char *argv[])
{
  js_func();
  return 0;
}

asmjs-test.js

mergeInto(LibraryManager.library, {
  js_func: function() {
    Module.print("Now we are in js side, let's call back to c side!");
    Module.ccall('c_func_calling_from_js', 'number', [], []);
  }
});

asmjs.out

$ emcc --js-library asmjs-test.js asmjs-test.c -s ASM_JS=1
$ node a.out.js
Now we are in js side, let's call back to c side!
Assertion failed: Cannot call unknown function c_func_calling_from_js (perhaps LLVM optimizations or closure removed it?):
Error
    at abort (/Users/rafael/develop/tmp/asmjs/a.out.js:491:32)
    at assert (/Users/rafael/develop/tmp/asmjs/a.out.js:498:5)
    at getCFunc (/Users/rafael/develop/tmp/asmjs/a.out.js:543:56)
    at Object.ccall (/Users/rafael/develop/tmp/asmjs/a.out.js:530:20)
    at _js_func (/Users/rafael/develop/tmp/asmjs/a.out.js:1929:14)
    at Object._main (/Users/rafael/develop/tmp/asmjs/a.out.js:2445:8)
    at Object.callMain (/Users/rafael/develop/tmp/asmjs/a.out.js:2542:25)
    at doRun (/Users/rafael/develop/tmp/asmjs/a.out.js:2574:20)
    at run (/Users/rafael/develop/tmp/asmjs/a.out.js:2598:12)
    at /Users/rafael/develop/tmp/asmjs/a.out.js:2620:13

/Users/rafael/develop/tmp/asmjs/a.out.js:493
  throw "Assertion: " + text;
                      ^
Assertion: Assertion failed: Cannot call unknown function c_func_calling_from_js (perhaps LLVM optimizations or closure removed it?)

normal.out

$ emcc --js-library asmjs-test.js asmjs-test.c
$ node a.out.js
Now we are in js side, let's call back to c side!
This is a c function calling from js!