diff --git a/lib/system/alloc.nim b/lib/system/alloc.nim
index 3a1d7b6664..3ebbc8c1e7 100644
--- a/lib/system/alloc.nim
+++ b/lib/system/alloc.nim
@@ -33,7 +33,54 @@ const doNotUnmap = not (defined(amd64) or defined(i386)) or
                    defined(windows) or defined(nimAllocNoUnmap)
 
 
-when defined(posix):
+when defined(emscripten):
+  const
+    PROT_READ  = 1             # page can be read
+    PROT_WRITE = 2             # page can be written
+    MAP_PRIVATE = 2'i32        # Changes are private
+
+  var MAP_ANONYMOUS {.importc: "MAP_ANONYMOUS", header: "<sys/mman.h>".}: cint
+  type 
+    PEmscriptenMMapBlock = ptr EmscriptenMMapBlock
+    EmscriptenMMapBlock {.pure, inheritable.} = object
+      realSize: int        # size of previous chunk; for coalescing
+      realPointer: pointer     # if < PageSize it is a small chunk
+
+  proc mmap(adr: pointer, len: int, prot, flags, fildes: cint,
+            off: int): pointer {.header: "<sys/mman.h>".}
+
+  proc munmap(adr: pointer, len: int) {.header: "<sys/mman.h>".}
+
+  proc osAllocPages(block_size: int): pointer {.inline.} =
+    let realSize = block_size + sizeof(EmscriptenMMapBlock) + PageSize + 1
+    result = mmap(nil, realSize, PROT_READ or PROT_WRITE,
+                             MAP_PRIVATE or MAP_ANONYMOUS, -1, 0)
+    if result == nil or result == cast[pointer](-1):
+      raiseOutOfMem()
+
+    let realPointer = result
+    let pos = cast[int](result)
+
+    # Convert pointer to PageSize correct one.
+    var new_pos = cast[ByteAddress](pos) +% (PageSize - (pos %% PageSize))
+    if (new_pos-pos)< sizeof(EmscriptenMMapBlock):
+      new_pos = new_pos +% PageSize
+    result = cast[pointer](new_pos)
+
+    var mmapDescrPos = cast[ByteAddress](result) -% sizeof(EmscriptenMMapBlock)
+
+    var mmapDescr = cast[EmscriptenMMapBlock](mmapDescrPos)
+    mmapDescr.realSize = realSize
+    mmapDescr.realPointer = realPointer
+
+    c_fprintf(c_stdout, "[Alloc] size %d %d realSize:%d realPos:%d\n", block_size, cast[int](result), realSize, cast[int](realPointer))
+
+  proc osDeallocPages(p: pointer, size: int) {.inline} =
+    var mmapDescrPos = cast[ByteAddress](p) -% sizeof(EmscriptenMMapBlock)
+    var mmapDescr = cast[EmscriptenMMapBlock](mmapDescrPos)
+    munmap(mmapDescr.realPointer, mmapDescr.realSize)
+
+elif defined(posix):
   const
     PROT_READ  = 1             # page can be read
     PROT_WRITE = 2             # page can be written
diff --git a/lib/system/gc_common.nim b/lib/system/gc_common.nim
index ceb3623784..47e8b4b1f7 100644
--- a/lib/system/gc_common.nim
+++ b/lib/system/gc_common.nim
@@ -95,7 +95,9 @@ proc setupForeignThreadGc*() =
 # ----------------- stack management --------------------------------------
 #  inspired from Smart Eiffel
 
-when defined(sparc):
+when defined(emscripten):
+  const stackIncreases = true
+elif defined(sparc):
   const stackIncreases = false
 elif defined(hppa) or defined(hp9000) or defined(hp9000s300) or
      defined(hp9000s700) or defined(hp9000s800) or defined(hp9000s820):
@@ -162,9 +164,9 @@ elif stackIncreases:
   proc isOnStack(p: pointer): bool =
     var stackTop {.volatile.}: pointer
     stackTop = addr(stackTop)
-    var a = cast[TAddress](gch.stackBottom)
-    var b = cast[TAddress](stackTop)
-    var x = cast[TAddress](p)
+    var a = cast[ByteAddress](gch.stackBottom)
+    var b = cast[ByteAddress](stackTop)
+    var x = cast[ByteAddress](p)
     result = a <=% x and x <=% b
 
   var
@@ -173,14 +175,14 @@ elif stackIncreases:
       # in a platform independent way
 
   template forEachStackSlot(gch, gcMark: expr) {.immediate, dirty.} =
-    var registers: C_JmpBuf
+    var registers {.noinit.}: C_JmpBuf
     if c_setjmp(registers) == 0'i32: # To fill the C stack with registers.
-      var max = cast[TAddress](gch.stackBottom)
-      var sp = cast[TAddress](addr(registers)) +% jmpbufSize -% sizeof(pointer)
+      var max = cast[ByteAddress](gch.stackBottom)
+      var sp = cast[ByteAddress](addr(registers)) +% jmpbufSize -% sizeof(pointer)
       # sp will traverse the JMP_BUF as well (jmp_buf size is added,
       # otherwise sp would be below the registers structure).
       while sp >=% max:
-        gcMark(gch, cast[ppointer](sp)[])
+        gcMark(gch, cast[PPointer](sp)[])
         sp = sp -% sizeof(pointer)
 
 else:
diff --git a/tests/gc/gcemscripten.nim b/tests/gc/gcemscripten.nim
new file mode 100644
index 0000000000..bbef13d98f
--- /dev/null
+++ b/tests/gc/gcemscripten.nim
@@ -0,0 +1,59 @@
+discard """
+  outputsub: "77\n77"
+"""
+
+## Check how GC/Alloc works in Emscripten
+import strutils
+
+type
+  X = ref XObj
+  XObj = object
+    name: string
+    value: int
+when defined(allow_print):
+  const print = true
+else:
+  const print = false
+
+proc myResult3*(i:int):X {.exportc.} =
+  if print: echo "3"
+  new(result)
+  if print: echo "3-2"
+  result.value = i
+
+proc myResult5*(i:int, x:X):X {.exportc.} =
+  if print: echo "5"
+  system.GC_fullCollect()
+  new(result)
+  if print: echo "5-2"
+  result.value = i
+  x.value = i+1
+  if result.value == x.value:
+    echo "This should not happen. Just allocated variable points to parameter"
+
+proc myResult2*(val: string, i: int): X {.exportc.} =
+  if print: echo "2-1"
+  result = myResult3(i)
+  if print: echo "2-2"
+  system.GC_fullCollect()
+  if print: echo "2-3"
+  var t = new(X)
+  if print: echo "2-4"
+  result.name = val
+  if t.name == "qwe":
+    echo "This should not happen. Variable is GC collected and new one on same place are allocated."
+  if print: echo "2-5"
+
+proc myResult4*(val: string, i: int): X {.exportc.} =
+  if print: echo "4-1"
+  result = myResult5(i, X())
+  if print: echo "4-2"
+
+var x = myResult2("qwe", 77)
+echo intToStr(x.value)
+
+var x2 = myResult4("qwe", 77)
+echo intToStr(x2.value)
+
+
+
diff --git a/tests/testament/categories.nim b/tests/testament/categories.nim
index 9de33acb1f..57b28620e4 100644
--- a/tests/testament/categories.nim
+++ b/tests/testament/categories.nim
@@ -124,6 +124,7 @@ proc gcTests(r: var TResults, cat: Category, options: string) =
     testSpec r, makeTest("tests/gc" / filename, options &
                   " -d:release --gc:markAndSweep", cat, actionRun)
 
+  test "gcemscripten"
   test "growobjcrash"
   test "gcbench"
   test "gcleak"