diff --git a/windows/native_exec/simple_x64.py b/windows/native_exec/simple_x64.py
index a034ba1..556b2c5 100644
--- a/windows/native_exec/simple_x64.py
+++ b/windows/native_exec/simple_x64.py
@@ -651,7 +651,11 @@ class Slash(object):
             raise ValueError("Missing arg for Slash")
         # Reuse all the MODRm logique with the reg as our self.reg
         # The sens of param is strange I need to fix the `reversed` logique
-        arg_consum, value, rex = ModRM([ModRM_REG__REG, ModRM_REG64__MEM], has_direction_bit=False).accept_arg(args[:1] + [self.reg] + args[1:], instr_state)
+        try:
+            arg_consum, value, rex = ModRM([ModRM_REG__REG, ModRM_REG64__MEM], has_direction_bit=False).accept_arg(args[:1] + [self.reg] + args[1:], instr_state)
+        except ValueError as e:
+            # Size mismatch
+            return None, None, None
         if value is None:
             return arg_consum, value, rex
         return arg_consum - 1, value, rex
@@ -855,7 +859,9 @@ class Lea(Instruction):
 
 class Mov(Instruction):
     default_32_bits = True
-    encoding = [(Mov_RAX_OFF64(),), (Mov_OFF64_RAX(),), (RawBits.from_int(8, 0x89), ModRM([ModRM_REG__REG, ModRM_REG64__MEM])),
+    encoding = [(Mov_RAX_OFF64(),), (Mov_OFF64_RAX(),),
+                (RawBits.from_int(8, 0xc7), Slash(0), Imm32()),
+                (RawBits.from_int(8, 0x89), ModRM([ModRM_REG__REG, ModRM_REG64__MEM])),
                 (RawBits.from_int(5, 0xb8 >> 3), X64RegisterSelector(), Imm64())]
 
 
diff --git a/windows/native_exec/simple_x86.py b/windows/native_exec/simple_x86.py
index 7aaccbf..c6eada9 100644
--- a/windows/native_exec/simple_x86.py
+++ b/windows/native_exec/simple_x86.py
@@ -483,6 +483,8 @@ class ControlRegisterModRM(object):
             return None, None
         reg = args[writecr]
         cr = args[not writecr]
+        if not isinstance(cr, str):
+            return None, None
         if not cr.lower().startswith("cr"):
             return None, None
         try:
@@ -646,6 +648,7 @@ class Sub(Instruction):
 
 class Mov(Instruction):
     encoding = [(RawBits.from_int(8, 0x89), ModRM([ModRM_REG__REG, ModRM_REG__MEM])),
+                (RawBits.from_int(8, 0xc7), Slash(0), Imm32()),
                 (RawBits.from_int(5, 0xb8 >> 3), X86RegisterSelector(), Imm32()),
                 (RawBits.from_int(16, 0x0f20), ControlRegisterModRM(writecr=False)),
                 (RawBits.from_int(16, 0x0f22), ControlRegisterModRM(writecr=True))]
@@ -747,7 +750,7 @@ class MultipleInstr(object):
 
     def get_code(self):
         if self.expected_labels:
-            raise ValueError("Unresolved labels: {self.expected_labels}".format(self=self))
+            raise ValueError("Unresolved labels: {0}".format(self.expected_labels.keys()))
         return b"".join([x[1].get_code() for x in sorted(self.instrs.items())])
 
     def add_instruction(self, instruction):
@@ -871,6 +874,38 @@ class MultipleInstr(object):
             self.add_instruction(other)
         return self
 
+
+def split_in_instruction(str):
+    for line in str.split("\n"):
+        if not line:
+            continue
+        for instr in line.split(";"):
+            if not instr:
+                continue
+            yield instr.strip()
+
+def assemble(str):
+    """Play test"""
+    shellcode = MultipleInstr()
+    for instr in split_in_instruction(str):
+        data = instr.split(" ", 1)
+        mnemo, args_raw = data[0], data[1:]
+        try:
+            instr_object = globals()[mnemo.capitalize()]
+        except:
+            raise ValueError("Unknow mnemonic <{0}>".format(mnemo))
+
+        args = []
+        if args_raw:
+            for arg in args_raw[0].split(","):
+                arg = arg.strip()
+                if (arg[0] == "[" or arg[2:4] == ":[") and arg[-1] == "]":
+                    print("MEM")
+                    arg = mem(arg)
+                args.append(arg)
+        shellcode += instr_object(*args)
+    return shellcode.get_code()
+
 # IDA : import windows.native_exec.simple_x86 as x86
 # IDA testing
 
diff --git a/windows/native_exec/test_simple_x64.py b/windows/native_exec/test_simple_x64.py
index f0c618f..bf02d6b 100644
--- a/windows/native_exec/test_simple_x64.py
+++ b/windows/native_exec/test_simple_x64.py
@@ -126,6 +126,8 @@ TestInstr(Mov)('R8', 0x1122334455667788)
 TestInstr(Mov)('RCX', -1)
 TestInstr(Mov, immediat_accepted=-1)('RCX', 0xffffffffffffffff)
 TestInstr(Mov)(mem('gs:[0x1122334455667788]'), 'RAX')
+TestInstr(Mov)(mem('[RAX]'), 0x11223344)
+TestInstr(Mov)(mem('[EAX]'), 0x11223344)
 
 TestInstr(And)('RCX', 'RBX')
 TestInstr(And)('RAX', 0x11223344)
diff --git a/windows/native_exec/test_simple_x86.py b/windows/native_exec/test_simple_x86.py
index 33a0b3b..fbf02e7 100644
--- a/windows/native_exec/test_simple_x86.py
+++ b/windows/native_exec/test_simple_x86.py
@@ -10,11 +10,15 @@ def disas(x):
 
 
 class TestInstr(object):
-    def __init__(self, instr_to_test, expected_result=None):
+    def __init__(self, instr_to_test, expected_result=None, debug=False):
         self.instr_to_test = instr_to_test
         self.expected_result = expected_result
+        self.debug = debug
 
     def __call__(self, *args):
+        if self.debug:
+            import pdb;pdb.set_trace()
+            pdb.DONE = True
         res = bytes(self.instr_to_test(*args).get_code())
         capres_list = disas(res)
         if len(capres_list) != 1:
@@ -107,6 +111,10 @@ TestInstr(Mov)('AX', mem('fs:[EAX + ECX * 4+0x30]'))
 TestInstr(Add)('EAX', 8)
 TestInstr(Add)('EAX', 0xffffffff)
 
+TestInstr(Add)(mem('[EAX]'), 10)
+TestInstr(Mov)('EAX', mem('fs:[0xfffc]'))
+TestInstr(Mov)(mem('fs:[0xfffc]'), 0)
+
 
 TestInstr(Sub)('ECX', 'ESP')
 TestInstr(Sub)('ECX', mem('[ESP]'))