diff --git a/src/cpu/core_dyn_x86/decoder.h b/src/cpu/core_dyn_x86/decoder.h
index 6bc6c109..8ef2330a 100644
--- a/src/cpu/core_dyn_x86/decoder.h
+++ b/src/cpu/core_dyn_x86/decoder.h
@@ -1589,8 +1589,7 @@ static void dyn_load_seg(SegNames seg,DynReg * src) {
 }
 
 static void dyn_load_seg_off_ea(SegNames seg) {
-	dyn_get_modrm();
-	if (GCC_UNLIKELY(decode.modrm.mod<3)) {
+	if (decode.modrm.mod<3) {
 		dyn_fill_ea();
 		gen_lea(DREG(TMPB),DREG(EA),0,0,decode.big_op ? 4:2);
 		dyn_read_word(DREG(TMPB),DREG(TMPB),false);
@@ -1666,7 +1665,7 @@ static void dyn_leave(void) {
 }
 
 static void dyn_segprefix(SegNames seg) {
-	if (GCC_UNLIKELY((Bitu)(decode.segprefix))) IllegalOption("dyn_segprefix");
+//	if (GCC_UNLIKELY((Bitu)(decode.segprefix))) IllegalOption("dyn_segprefix");
 	decode.segprefix=&DynRegs[G_ES+seg];
 }
 
@@ -1988,8 +1987,16 @@ restart_prefix:
 			/* Imul Ev,Gv */
 			case 0xaf:dyn_imul_gvev(0);break;
 			/* LFS,LGS */
-			case 0xb4:dyn_load_seg_off_ea(fs);break;
-			case 0xb5:dyn_load_seg_off_ea(gs);break;
+			case 0xb4:
+				dyn_get_modrm();
+				if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+				dyn_load_seg_off_ea(fs);
+				break;
+			case 0xb5:
+				dyn_get_modrm();
+				if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+				dyn_load_seg_off_ea(gs);
+				break;
 			/* MOVZX Gv,Eb/Ew */
 			case 0xb6:dyn_mov_ev_gb(false);break;
 			case 0xb7:dyn_mov_ev_gw(false);break;
@@ -2240,9 +2247,18 @@ restart_prefix:
 		//RET near Iw / Ret
 		case 0xc2:dyn_ret_near(decode_fetchw());goto finish_block;
 		case 0xc3:dyn_ret_near(0);goto finish_block;
-		//LES/LDS
-		case 0xc4:dyn_load_seg_off_ea(es);break;
-		case 0xc5:dyn_load_seg_off_ea(ds);break;
+		//LES
+		case 0xc4:
+			dyn_get_modrm();
+			if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+			dyn_load_seg_off_ea(es);
+			break;
+		//LDS
+		case 0xc5:
+			dyn_get_modrm();
+			if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+			dyn_load_seg_off_ea(ds);
+			break;
 		// MOV Eb/Ev,Ib/Iv
 		case 0xc6:dyn_mov_ebib();break;
 		case 0xc7:dyn_mov_eviv();break;
diff --git a/src/cpu/core_dynrec/decoder.h b/src/cpu/core_dynrec/decoder.h
index 143e50a1..76603912 100644
--- a/src/cpu/core_dynrec/decoder.h
+++ b/src/cpu/core_dynrec/decoder.h
@@ -218,8 +218,18 @@ restart_prefix:
 
 				case 0xaf:dyn_imul_gvev(0);break;
 
-				case 0xb4:dyn_load_seg_off_ea(DRC_SEG_FS);break;
-				case 0xb5:dyn_load_seg_off_ea(DRC_SEG_GS);break;
+				// lfs
+				case 0xb4:
+					dyn_get_modrm();
+					if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+					dyn_load_seg_off_ea(DRC_SEG_FS);
+					break;
+				// lgs
+				case 0xb5:
+					dyn_get_modrm();
+					if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+					dyn_load_seg_off_ea(DRC_SEG_GS);
+					break;
 
 				// zero-extending moves
 				case 0xb6:dyn_movx_ev_gb(false);break;
@@ -413,8 +423,17 @@ restart_prefix:
 		case 0xc2:dyn_ret_near(decode_fetchw());goto finish_block;
 		case 0xc3:dyn_ret_near(0);goto finish_block;
 
-		case 0xc4:dyn_load_seg_off_ea(DRC_SEG_ES);break;
-		case 0xc5:dyn_load_seg_off_ea(DRC_SEG_DS);break;
+		// les
+		case 0xc4:
+			dyn_get_modrm();
+			if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+			dyn_load_seg_off_ea(DRC_SEG_ES);
+			break;
+		// lds
+		case 0xc5:
+			dyn_get_modrm();
+			if (GCC_UNLIKELY(decode.modrm.mod==3)) goto illegalopcode;
+			dyn_load_seg_off_ea(DRC_SEG_DS);break;
 
 		// 'mov []/reg8/16/32,imm8/16/32'
 		case 0xc6:dyn_dop_ebib_mov();break;
diff --git a/src/cpu/core_dynrec/decoder_opcodes.h b/src/cpu/core_dynrec/decoder_opcodes.h
index 1771f989..cbf0625e 100644
--- a/src/cpu/core_dynrec/decoder_opcodes.h
+++ b/src/cpu/core_dynrec/decoder_opcodes.h
@@ -453,7 +453,7 @@ static void dyn_pop_ev(void) {
 
 
 static void dyn_segprefix(Bit8u seg) {
-	if (GCC_UNLIKELY(decode.seg_prefix_used)) IllegalOptionDynrec("dyn_segprefix");
+//	if (GCC_UNLIKELY(decode.seg_prefix_used)) IllegalOptionDynrec("dyn_segprefix");
 	decode.seg_prefix=seg;
 	decode.seg_prefix_used=true;
 }
@@ -472,7 +472,6 @@ static void dyn_segprefix(Bit8u seg) {
 }
 
 static void dyn_load_seg_off_ea(Bit8u seg) {
-	dyn_get_modrm();
 	if (decode.modrm.mod<3) {
 		dyn_fill_ea(FC_ADDR);
 		gen_protect_addr_reg();