diff --git a/windows/native_exec/simple_x64.py b/windows/native_exec/simple_x64.py
index 8063a34..14a0bc5 100644
--- a/windows/native_exec/simple_x64.py
+++ b/windows/native_exec/simple_x64.py
@@ -908,7 +908,7 @@ class Lea(Instruction):
 class Mov(Instruction):
     default_32_bits = True
     encoding = [(Mov_RAX_OFF64(),), (Mov_OFF64_RAX(),),
-                (RawBits.from_int(8, 0xc7), Slash(0), AnyImm32()),
+                (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/test_simple_x64.py b/windows/native_exec/test_simple_x64.py
index 953c772..128b5e1 100644
--- a/windows/native_exec/test_simple_x64.py
+++ b/windows/native_exec/test_simple_x64.py
@@ -133,6 +133,10 @@ TestInstr(Mov)('RAX', mem('[0x1122334455667788]'))
 TestInstr(Mov)('RAX', mem('gs:[0x1122334455667788]'))
 TestInstr(Mov)('RAX', mem('gs:[0x60]'))
 TestInstr(Mov)('RCX', 0x1122334455667788)
+TestInstr(Mov)('RCX', -1)
+TestInstr(Mov)('RCX', -0x1000)
+TestInstr(Mov)('RCX', 0xffffffff)
+TestInstr(Mov)('RAX', 0xffffffff)
 TestInstr(Mov)('R8', 0x1122334455667788)
 TestInstr(Mov)('RCX', -1)
 TestInstr(Mov, immediat_accepted=-1)('RCX', 0xffffffffffffffff)