diff --git a/gen/x86_table.js b/gen/x86_table.js
index 731840d4..9827c630 100644
--- a/gen/x86_table.js
+++ b/gen/x86_table.js
@@ -246,7 +246,7 @@ const encodings = [
     { opcode: 0xF2AD, block_boundary: 1, custom: 1, is_string: 1, os: 1, },
     { opcode: 0xF3AD, block_boundary: 1, custom: 1, is_string: 1, os: 1, },
 
-    { opcode: 0xAE, block_boundary: 1, custom: 1, is_string: 1, },
+    { opcode: 0xAE, block_boundary: 0, custom: 1, is_string: 1, },
     { opcode: 0xF2AE, block_boundary: 1, custom: 1, is_string: 1, },
     { opcode: 0xF3AE, block_boundary: 1, custom: 1, is_string: 1, },
     { opcode: 0xAF, block_boundary: 1, custom: 1, is_string: 1, os: 1, },
diff --git a/src/rust/cpu/string.rs b/src/rust/cpu/string.rs
index 0cbcbda3..738bd6ce 100644
--- a/src/rust/cpu/string.rs
+++ b/src/rust/cpu/string.rs
@@ -593,7 +593,6 @@ pub unsafe fn scasw_repnz(is_asize_32: bool) {
 pub unsafe fn scasd_repnz(is_asize_32: bool) {
     string_instruction(is_asize_32, 0, Instruction::Scas, Size::D, Rep::NZ)
 }
-#[no_mangle]
 pub unsafe fn scasb_no_rep(is_asize_32: bool) {
     string_instruction(is_asize_32, 0, Instruction::Scas, Size::B, Rep::None)
 }
diff --git a/src/rust/jit_instructions.rs b/src/rust/jit_instructions.rs
index d0fc7681..fb933ad7 100644
--- a/src/rust/jit_instructions.rs
+++ b/src/rust/jit_instructions.rs
@@ -8,7 +8,7 @@ use cpu::cpu::{
 };
 use cpu::global_pointers;
 use jit::{Instruction, InstructionOperand, JitContext};
-use modrm::{jit_add_seg_offset, ModrmByte};
+use modrm::{jit_add_seg_offset, jit_add_seg_offset_no_override, ModrmByte};
 use prefix::SEG_PREFIX_ZERO;
 use prefix::{PREFIX_66, PREFIX_67, PREFIX_F2, PREFIX_F3};
 use regs;
@@ -4489,6 +4489,36 @@ fn gen_string_ins(ctx: &mut JitContext, ins: String, size: u8, prefix: u8) {
                 }
                 return;
             },
+            (String::SCAS, 8) => {
+                if ctx.cpu.asize_32() {
+                    codegen::gen_get_reg32(ctx, regs::EDI);
+                }
+                else {
+                    codegen::gen_get_reg16(ctx, regs::EDI);
+                }
+                jit_add_seg_offset_no_override(ctx, regs::ES);
+                let address_local = ctx.builder.set_new_local();
+                codegen::gen_safe_read8(ctx, &address_local);
+                ctx.builder.free_local(address_local);
+                let value = ctx.builder.set_new_local();
+                gen_cmp8(
+                    ctx,
+                    &ctx.reg(regs::EAX),
+                    &LocalOrImmediate::WasmLocal(&value),
+                );
+                ctx.builder.free_local(value);
+
+                codegen::gen_get_reg32(ctx, regs::EDI);
+                get_direction(ctx);
+                ctx.builder.add_i32();
+                if ctx.cpu.asize_32() {
+                    codegen::gen_set_reg32(ctx, regs::EDI);
+                }
+                else {
+                    codegen::gen_set_reg16(ctx, regs::EDI);
+                }
+                return;
+            },
             _ => {},
         }
     }
diff --git a/src/rust/modrm.rs b/src/rust/modrm.rs
index 41a5383a..4cffb346 100644
--- a/src/rust/modrm.rs
+++ b/src/rust/modrm.rs
@@ -254,9 +254,17 @@ fn can_optimize_get_seg(ctx: &mut JitContext, segment: u32) -> bool {
 
 pub fn jit_add_seg_offset(ctx: &mut JitContext, default_segment: u32) {
     let prefix = ctx.cpu.prefixes & PREFIX_MASK_SEGMENT;
-    let seg = if prefix != 0 { prefix - 1 } else { default_segment };
 
-    if can_optimize_get_seg(ctx, seg) || prefix == SEG_PREFIX_ZERO {
+    if prefix == SEG_PREFIX_ZERO {
+        return;
+    }
+
+    let seg = if prefix != 0 { prefix - 1 } else { default_segment };
+    jit_add_seg_offset_no_override(ctx, seg);
+}
+
+pub fn jit_add_seg_offset_no_override(ctx: &mut JitContext, seg: u32) {
+    if can_optimize_get_seg(ctx, seg) {
         codegen::gen_profiler_stat_increment(ctx.builder, profiler::stat::SEG_OFFSET_OPTIMISED);
         return;
     }