diff --git a/src/arch.c b/src/arch.c
index d1ead4a..ff4ab54 100644
--- a/src/arch.c
+++ b/src/arch.c
@@ -282,6 +282,10 @@ static int _call_operands_immediate(ArchOperandDefinition definition,
 	value >>= size;
 	if(value > 0)
 		return -1;
+	/* check if it is signed */
+	if(operand->value.immediate.negative
+			&& !(AO_GET_FLAGS(definition) & AOF_SIGNED))
+		return -1;
 	return 0;
 }
 
diff --git a/src/arch/i386.c b/src/arch/i386.c
index f5a6084..edbeaae 100644
--- a/src/arch/i386.c
+++ b/src/arch/i386.c
@@ -175,19 +175,20 @@ static int _write_dregister(ArchPlugin * plugin, uint32_t * i,
 static int _write_immediate(ArchPlugin * plugin,
 		ArchOperandDefinition definition, ArchOperand * operand)
 {
+	uint64_t value = operand->value.immediate.value;
+
+	if(AO_GET_FLAGS(definition) & AOF_SIGNED)
+		value = -value;
 	switch(AO_GET_SIZE(definition) >> 3)
 	{
 		case 0:
 			return 0;
 		case sizeof(uint8_t):
-			return _write_immediate8(plugin,
-					operand->value.immediate.value);
+			return _write_immediate8(plugin, value);
 		case sizeof(uint16_t):
-			return _write_immediate16(plugin,
-					operand->value.immediate.value);
+			return _write_immediate16(plugin, value);
 		case sizeof(uint32_t):
-			return _write_immediate32(plugin,
-					operand->value.immediate.value);
+			return _write_immediate32(plugin, value);
 		default:
 			return -1;
 	}
diff --git a/src/arch/i386.ins b/src/arch/i386.ins
index 73dba06..f76bfd0 100644
--- a/src/arch/i386.ins
+++ b/src/arch/i386.ins
@@ -36,6 +36,8 @@
 #define OP_RMW_RW	AO_REGISTER(AOF_I386_MODRM, W, 0)	/* 0xc0 */
 
 /* immediate values */
+#define OP_S8		AO_IMMEDIATE(AOF_SIGNED, 0, 8)
+#define OP_SW		AO_IMMEDIATE(AOF_SIGNED, 0, W)
 #define OP_U8		AO_IMMEDIATE(0, 0, 8)
 #define OP_UW		AO_IMMEDIATE(0, 0, W)
 
@@ -60,19 +62,24 @@
 { "adc",	0x12,		OP1F, OP_RM8_R8_R,OP_RM8_R8_R,AOT_NONE	},
 #endif
 /* ADC		0x14 ib		1     al          imm8			*/
-{ "adc",	0x14,		OP1F, OP_al,	  OP_U8,     AOT_NONE	},
+{ "adc",	0x14,		OP1F, OP_al,	  OP_S8,     AOT_NONE	},
 /* ADC		0x15 iW		1     AX          immW			*/
-{ "adc",	0x15,		OP1F, OP_AX,	  OP_UW,     AOT_NONE	},
+{ "adc",	0x15,		OP1F, OP_AX,	  OP_SW,     AOT_NONE	},
 /* ADC		0x80 /2 ib	1     r/m8        imm8			*/
-{ "adc",	0x80,		OP1F, OP_RM8_D0+2,OP_U8,     AOT_NONE	},
-{ "adc",	0x80,		OP1F, OP_RM8_D8+2,OP_U8,     AOT_NONE	},
-{ "adc",	0x80,		OP1F, OP_RM8_DW+2,OP_U8,     AOT_NONE	},
-{ "adc",	0x80,		OP1F, OP_RM8_R8+2,OP_U8,     AOT_NONE	},
+{ "adc",	0x80,		OP1F, OP_RM8_D0+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x80,		OP1F, OP_RM8_D8+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x80,		OP1F, OP_RM8_DW+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x80,		OP1F, OP_RM8_R8+2,OP_S8,     AOT_NONE	},
 /* ADC		0x81 /2 iW	1     r/m8        imm8			*/
-{ "adc",	0x81,		OP1F, OP_RMW_D0+2,OP_UW,     AOT_NONE	},
-{ "adc",	0x81,		OP1F, OP_RMW_D8+2,OP_UW,     AOT_NONE	},
-{ "adc",	0x81,		OP1F, OP_RMW_DW+2,OP_UW,     AOT_NONE	},
-{ "adc",	0x81,		OP1F, OP_RMW_RW+2,OP_UW,     AOT_NONE	},
+{ "adc",	0x81,		OP1F, OP_RMW_D0+2,OP_SW,     AOT_NONE	},
+{ "adc",	0x81,		OP1F, OP_RMW_D8+2,OP_SW,     AOT_NONE	},
+{ "adc",	0x81,		OP1F, OP_RMW_DW+2,OP_SW,     AOT_NONE	},
+{ "adc",	0x81,		OP1F, OP_RMW_RW+2,OP_SW,     AOT_NONE	},
+/* ADC		0x83 /2 i8	1     r/m8        imm8			*/
+{ "adc",	0x83,		OP1F, OP_RMW_D0+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x83,		OP1F, OP_RMW_D8+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x83,		OP1F, OP_RMW_DW+2,OP_S8,     AOT_NONE	},
+{ "adc",	0x83,		OP1F, OP_RMW_RW+2,OP_S8,     AOT_NONE	},
 /* ADD		0x04 ib		1     al          imm8			*/
 { "add",	0x04,		OP1F, OP_al,	  OP_U8,     AOT_NONE	},
 /* ADD		0x05 iW		1     AX          immW			*/
@@ -82,7 +89,7 @@
 { "add",	0x80,		OP1F, OP_RM8_D8+0,OP_U8,     AOT_NONE	},
 { "add",	0x80,		OP1F, OP_RM8_DW+0,OP_U8,     AOT_NONE	},
 { "add",	0x80,		OP1F, OP_RM8_R8+0,OP_U8,     AOT_NONE	},
-/* ADC		0x81 /0 iW	1     r/m8        imm8			*/
+/* ADD		0x81 /0 iW	1     r/m8        imm8			*/
 { "add",	0x81,		OP1F, OP_RMW_D0+0,OP_UW,     AOT_NONE	},
 { "add",	0x81,		OP1F, OP_RMW_D8+0,OP_UW,     AOT_NONE	},
 { "add",	0x81,		OP1F, OP_RMW_DW+0,OP_UW,     AOT_NONE	},
diff --git a/test/i386.S b/test/i386.S
index 2a90751..6aca98d 100644
--- a/test/i386.S
+++ b/test/i386.S
@@ -26,6 +26,7 @@
 						/* 81 93 19 18 17 16 4b	*/
 						/* 4a 49 48		*/
 	adc	%ecx, $0x45464748		/* 81 d1 45 46 47 48	*/
+	adc	[%eax], -$0x02			/* 83 10 fe		*/
 	/* ADD */
 	add	%al, $0x40			/* 04 40		*/
 	add	%eax, $0x41424344		/* 05 44 43 42 41	*/