diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 0c1ac6982d2..07687ef8b58 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1345,6 +1345,8 @@ unsigned FastISel::FastEmitInst_extractsubreg(MVT RetVT,
   unsigned ResultReg = createResultReg(TLI.getRegClassFor(RetVT));
   assert(TargetRegisterInfo::isVirtualRegister(Op0) &&
          "Cannot yet extract from physregs");
+  const TargetRegisterClass *RC = MRI.getRegClass(Op0);
+  MRI.constrainRegClass(Op0, TRI.getSubClassWithSubReg(RC, Idx));
   BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt,
           DL, TII.get(TargetOpcode::COPY), ResultReg)
     .addReg(Op0, getKillRegState(Op0IsKill), Idx);
diff --git a/test/CodeGen/X86/fast-isel.ll b/test/CodeGen/X86/fast-isel.ll
index c88d52968dd..9d9a520c6a2 100644
--- a/test/CodeGen/X86/fast-isel.ll
+++ b/test/CodeGen/X86/fast-isel.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -fast-isel -fast-isel-abort -march=x86 -mattr=sse2
-; RUN: llc < %s -fast-isel -fast-isel-abort -mtriple=x86_64-apple-darwin10
+; RUN: llc < %s -fast-isel -fast-isel-abort -verify-machineinstrs -march=x86 -mattr=sse2
+; RUN: llc < %s -fast-isel -fast-isel-abort -verify-machineinstrs -mtriple=x86_64-apple-darwin10
 
 ; This tests very minimal fast-isel functionality.