diff --git a/etcdserver2/request.pb.go b/etcdserver2/request.pb.go
index f8ff72fe5..d2a4bd18c 100644
--- a/etcdserver2/request.pb.go
+++ b/etcdserver2/request.pb.go
@@ -35,7 +35,7 @@ type Request struct {
 	Dir              bool   `protobuf:"varint,5,req,name=dir" json:"dir"`
 	PrevValue        string `protobuf:"bytes,6,req,name=prevValue" json:"prevValue"`
 	PrevIndex        uint64 `protobuf:"varint,7,req,name=prevIndex" json:"prevIndex"`
-	PrevExists       bool   `protobuf:"varint,8,req,name=prevExists" json:"prevExists"`
+	PrevExists       *bool  `protobuf:"varint,8,req,name=prevExists" json:"prevExists,omitempty"`
 	Expiration       int64  `protobuf:"varint,9,req,name=expiration" json:"expiration"`
 	Wait             bool   `protobuf:"varint,10,req,name=wait" json:"wait"`
 	Since            uint64 `protobuf:"varint,11,req,name=since" json:"since"`
@@ -220,7 +220,8 @@ func (m *Request) Unmarshal(data []byte) error {
 					break
 				}
 			}
-			m.PrevExists = bool(v != 0)
+			b := bool(v != 0)
+			m.PrevExists = &b
 		case 9:
 			if wireType != 0 {
 				return code_google_com_p_gogoprotobuf_proto.ErrWrongType
@@ -339,7 +340,9 @@ func (m *Request) Size() (n int) {
 	l = len(m.PrevValue)
 	n += 1 + l + sovRequest(uint64(l))
 	n += 1 + sovRequest(uint64(m.PrevIndex))
-	n += 2
+	if m.PrevExists != nil {
+		n += 2
+	}
 	n += 1 + sovRequest(uint64(m.Expiration))
 	n += 2
 	n += 1 + sovRequest(uint64(m.Since))
@@ -409,14 +412,16 @@ func (m *Request) MarshalTo(data []byte) (n int, err error) {
 	data[i] = 0x38
 	i++
 	i = encodeVarintRequest(data, i, uint64(m.PrevIndex))
-	data[i] = 0x40
-	i++
-	if m.PrevExists {
-		data[i] = 1
-	} else {
-		data[i] = 0
+	if m.PrevExists != nil {
+		data[i] = 0x40
+		i++
+		if *m.PrevExists {
+			data[i] = 1
+		} else {
+			data[i] = 0
+		}
+		i++
 	}
-	i++
 	data[i] = 0x48
 	i++
 	i = encodeVarintRequest(data, i, uint64(m.Expiration))
diff --git a/etcdserver2/request.proto b/etcdserver2/request.proto
index 69203365d..eaac41e2a 100644
--- a/etcdserver2/request.proto
+++ b/etcdserver2/request.proto
@@ -15,7 +15,7 @@ message Request {
 	required bool   dir        =  5 [(gogoproto.nullable) = false];
 	required string prevValue  =  6 [(gogoproto.nullable) = false];
 	required uint64  prevIndex  =  7 [(gogoproto.nullable) = false];
-	required bool   prevExists =  8 [(gogoproto.nullable) = false];
+	required bool   prevExists =  8 [(gogoproto.nullable) = true];
 	required int64  expiration =  9 [(gogoproto.nullable) = false];
 	required bool   wait       = 10 [(gogoproto.nullable) = false];
 	required uint64  since      = 11 [(gogoproto.nullable) = false];
diff --git a/etcdserver2/server.go b/etcdserver2/server.go
index 9dfff8531..5c7acbea2 100644
--- a/etcdserver2/server.go
+++ b/etcdserver2/server.go
@@ -119,13 +119,18 @@ func (s *Server) apply(ctx context.Context, e raft.Entry) (*store.Event, error)
 	case "POST":
 		return s.st.Create(r.Path, r.Dir, r.Val, true, expr)
 	case "PUT":
+		exists, set := getBool(r.PrevExists)
 		switch {
-		case r.PrevExists:
-			return s.st.Update(r.Path, r.Val, expr)
+		case set:
+			if exists {
+				return s.st.Update(r.Path, r.Val, expr)
+			} else {
+				return s.st.Create(r.Path, r.Dir, r.Val, false, expr)
+			}
 		case r.PrevIndex > 0 || r.PrevValue != "":
 			return s.st.CompareAndSwap(r.Path, r.PrevValue, r.PrevIndex, r.Val, expr)
 		default:
-			return s.st.Create(r.Path, r.Dir, r.Val, false, expr)
+			return s.st.Set(r.Path, r.Dir, r.Val, expr)
 		}
 	case "DELETE":
 		switch {
@@ -138,3 +143,10 @@ func (s *Server) apply(ctx context.Context, e raft.Entry) (*store.Event, error)
 		return nil, ErrUnknownMethod
 	}
 }
+
+func getBool(v *bool) (vv bool, set bool) {
+	if v == nil {
+		return false, false
+	}
+	return *v, true
+}