diff --git a/src/disasm.rs b/src/disasm.rs
index 68e3160..358fb39 100644
--- a/src/disasm.rs
+++ b/src/disasm.rs
@@ -12,7 +12,7 @@ use crate::{
 };
 use crate::{modrm_8b_register, modrm_16b_register, modrm_sregister};
 use core::fmt;
-use std::{fs::File, io::Read, process::exit};
+use std::{fs::File, io::Read};
 
 #[derive(Debug)]
 /// Generic errors, which are encountered during parsing.
@@ -820,6 +820,7 @@ impl Disassembler {
                 0xEE => Mnemonic::OUT_ALDX,
                 0xEF => Mnemonic::OUT_AXDX,
 
+                0xF0 => Mnemonic::LOCK,
                 0xF1 => return Err(DisasmError::OpcodeUndefined(opcode)),
 
                 0xF2 => Mnemonic::REPNZ,
@@ -872,13 +873,6 @@ impl Disassembler {
                         _ => return Err(DisasmError::IllegalGroupMnemonic(5, reg)),
                     }
                 }
-
-                _ => {
-                    eprintln!("Encountered unknown instruction '0x{:x}'", opcode);
-                    eprintln!("Offset might be misaligned and data is being interpreted.");
-                    eprintln!("Existing to avoid further misinterpretation...");
-                    exit(1);
-                }
             };
 
             // Save parsed instruction
diff --git a/src/instructions.rs b/src/instructions.rs
index 32bcdfb..8b59c5d 100644
--- a/src/instructions.rs
+++ b/src/instructions.rs
@@ -295,6 +295,7 @@ pub enum Mnemonic {
     AAD(Byte),
     // MISC
     XLAT,
+    LOCK,
 }
 
 impl fmt::Display for Mnemonic {
@@ -533,6 +534,8 @@ impl fmt::Display for Mnemonic {
 
             Self::XLAT => write!(f, "xlat"),
 
+            Self::LOCK => write!(f, "lock"),
+
             _ => write!(f, "??? ??, ??"),
         }
     }