1 files changed, 4 insertions, 0 deletions
diff --git a/src/long_mode/mod.rs b/src/long_mode/mod.rs
index 125716f..254ccc7 100644
--- a/src/long_mode/mod.rs
+++ b/src/long_mode/mod.rs
@@ -9133,6 +9133,10 @@ fn unlikely_operands<T: Reader<<Arch as yaxpeax_arch::Arch>::Address, <Arch as y
             }
         }
         OperandCode::ModRM_0x0f01 => {
+            if instruction.prefixes.rep() || instruction.prefixes.repnz() {
+                return Err(DecodeError::InvalidOperand);
+            }
+
             let opwidth = imm_width_from_prefixes_64(SizeCode::vq, instruction.prefixes);
             let modrm = read_modrm(words)?;
             let r = (modrm >> 3) & 7;