diff --git a/lib/CodeGen/MachineVerifier.cpp b/lib/CodeGen/MachineVerifier.cpp
index a202750..20dbe11 100644
--- a/lib/CodeGen/MachineVerifier.cpp
+++ b/lib/CodeGen/MachineVerifier.cpp
@@ -634,7 +634,7 @@
   if (MONum < MCID.getNumDefs()) {
     if (!MO->isReg())
       report("Explicit definition must be a register", MO, MONum);
-    else if (!MO->isDef())
+    else if (!MO->isDef() && !MCOI.isOptionalDef())
       report("Explicit definition marked as use", MO, MONum);
     else if (MO->isImplicit())
       report("Explicit definition marked as implicit", MO, MONum);