diff --git a/llvm/lib/Target/X86/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/X86MCCodeEmitter.cpp
index 5d745d24bdfb..898592eacb43 100644
--- a/llvm/lib/Target/X86/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/X86MCCodeEmitter.cpp
@@ -542,14 +542,9 @@ EncodeInstruction(const MCInst &MI, raw_ostream &OS,
     // FIXME: This is terrible, they should get proper encoding bits in TSFlags.
     if (Opcode == X86::LFENCE || Opcode == X86::MFENCE ||
         Opcode == X86::MONITOR || Opcode == X86::MWAIT) {
-      EmitByte(ModRMByte(3, (TSFlags & X86II::FormMask)-X86II::MRM0r, 0),
+      EmitByte(ModRMByte(3, (TSFlags & X86II::FormMask)-X86II::MRM0r,
+                         Opcode == X86::MWAIT),
                CurByte, OS);
-
-      switch (Opcode) {
-      default: break;
-      case X86::MONITOR: EmitByte(0xC8, CurByte, OS); break;
-      case X86::MWAIT:   EmitByte(0xC9, CurByte, OS); break;
-      }
     } else {
       EmitRegModRMByte(MI.getOperand(CurOp++),
                        (TSFlags & X86II::FormMask)-X86II::MRM0r,
diff --git a/llvm/test/MC/AsmParser/X86/x86_32-new-encoder.s b/llvm/test/MC/AsmParser/X86/x86_32-new-encoder.s
new file mode 100644
index 000000000000..5c47885cf6d7
--- /dev/null
+++ b/llvm/test/MC/AsmParser/X86/x86_32-new-encoder.s
@@ -0,0 +1,14 @@
+// RUN: llvm-mc -triple i386-unknown-unknown --show-encoding --enable-new-x86-encoder %s | FileCheck %s
+
+	lfence
+// CHECK: lfence
+// CHECK: encoding: [0x0f,0xae,0xe8]
+	mfence
+// CHECK: mfence
+// CHECK: encoding: [0x0f,0xae,0xf0]
+	monitor
+// CHECK: monitor
+// CHECK: encoding: [0x0f,0x01,0xc8]
+	mwait
+// CHECK: mwait
+// CHECK: encoding: [0x0f,0x01,0xc9]
\ No newline at end of file