diff --git a/encode_compile.go b/encode_compile.go
index 23284cd..9c1792d 100644
--- a/encode_compile.go
+++ b/encode_compile.go
@@ -765,10 +765,10 @@ func (e *Encoder) anonymousStructFieldPairMap(typ *rtype, tags structTags, named
 		} else if op != f.op {
 			if existsKey {
 				f.op = opStructFieldAnonymousHead
-			} else {
+			} else if named == "" {
 				f.op = op
 			}
-		} else if f.op == opStructEnd {
+		} else if named == "" && f.op == opStructEnd {
 			f.op = opStructAnonymousEnd
 		} else if existsKey {
 			diff := f.nextField.displayIdx - f.displayIdx
@@ -808,9 +808,9 @@ func (e *Encoder) anonymousStructFieldPairMap(typ *rtype, tags structTags, named
 }
 
 func (e *Encoder) optimizeConflictAnonymousFields(anonymousFields map[string][]structFieldPair) {
-	fmt.Printf("anonymousFields = %+v\n", anonymousFields)
+	//fmt.Printf("anonymousFields = %+v\n", anonymousFields)
 	removedFields := map[*opcode]struct{}{}
-	for name, fieldPairs := range anonymousFields {
+	for _, fieldPairs := range anonymousFields {
 		if len(fieldPairs) == 1 {
 			continue
 		}
@@ -823,24 +823,24 @@ func (e *Encoder) optimizeConflictAnonymousFields(anonymousFields map[string][]s
 				if !fieldPair.linked {
 					if fieldPair.prevField == nil {
 						// head operation
-						fmt.Println("omit:", fieldPair.curField.displayKey)
+						//fmt.Println("omit:", fieldPair.curField.displayKey)
 						fieldPair.curField.op = opStructFieldAnonymousHead
 					} else {
-						fmt.Println("remove", name)
+						//fmt.Println("remove", name)
 						diff := fieldPair.curField.nextField.displayIdx - fieldPair.curField.displayIdx
-						fmt.Println("link:", fieldPair.prevField.displayKey, "=>", fieldPair.curField.nextField.displayKey)
-						fmt.Println("diff = ", diff)
+						//fmt.Println("link:", fieldPair.prevField.displayKey, "=>", fieldPair.curField.nextField.displayKey)
+						//fmt.Println("diff = ", diff)
 						for i := 0; i < diff; i++ {
 							fieldPair.curField.nextField.decOpcodeIndex()
 						}
-						fmt.Println("cur.nextField")
-						fmt.Println(fieldPair.curField.nextField.dump())
-						fmt.Println("===========")
+						//fmt.Println("cur.nextField")
+						//fmt.Println(fieldPair.curField.nextField.dump())
+						//fmt.Println("===========")
 						removedFields[fieldPair.curField] = struct{}{}
 						linkPrevToNextField(fieldPair.curField, removedFields)
-						fmt.Println("linked. prevField")
-						fmt.Println(fieldPair.prevField.dump())
-						fmt.Println("===========")
+						//fmt.Println("linked. prevField")
+						//fmt.Println(fieldPair.prevField.dump())
+						//fmt.Println("===========")
 						// tagggedPairs に入れた方にもこの結果を反映させないといけない
 					}
 					fieldPair.linked = true
@@ -854,13 +854,13 @@ func (e *Encoder) optimizeConflictAnonymousFields(anonymousFields map[string][]s
 						// head operation
 						fieldPair.curField.op = opStructFieldAnonymousHead
 					} else {
-						fmt.Println("TAGGED PAIRS REMOVE")
-						fmt.Println("remove", name)
-						fmt.Println("removedFields = ", removedFields)
-						fmt.Printf("prev = %p cur = %p next = %p\n", fieldPair.curField.prevField, fieldPair.curField, fieldPair.curField.nextField)
+						//fmt.Println("TAGGED PAIRS REMOVE")
+						//fmt.Println("remove", name)
+						//fmt.Println("removedFields = ", removedFields)
+						//fmt.Printf("prev = %p cur = %p next = %p\n", fieldPair.curField.prevField, fieldPair.curField, fieldPair.curField.nextField)
 						diff := fieldPair.curField.nextField.displayIdx - fieldPair.curField.displayIdx
-						fmt.Println("link:", fieldPair.prevField.displayKey, "=>", fieldPair.curField.nextField.displayKey)
-						fmt.Println("diff = ", diff)
+						//fmt.Println("link:", fieldPair.prevField.displayKey, "=>", fieldPair.curField.nextField.displayKey)
+						//fmt.Println("diff = ", diff)
 						removedFields[fieldPair.curField] = struct{}{}
 						for i := 0; i < diff; i++ {
 							fieldPair.curField.nextField.decOpcodeIndex()
@@ -1035,23 +1035,23 @@ func (e *Encoder) compileStruct(ctx *encodeCompileContext, isPtr bool) (*opcode,
 
 	head.end = structEndCode
 	code.next = structEndCode
-
-	fmt.Println("head")
-	fmt.Println(head.dump())
-	fmt.Println("===============")
-
+	/*
+		fmt.Println("head")
+		fmt.Println(head.dump())
+		fmt.Println("===============")
+	*/
 	e.optimizeConflictAnonymousFields(anonymousFields)
-
-	fmt.Println("remove conflicted key head")
-	fmt.Println(head.dump())
-	fmt.Println("===============")
-
+	/*
+		fmt.Println("remove conflicted key head")
+		fmt.Println(head.dump())
+		fmt.Println("===============")
+	*/
 	e.optimizeAnonymousFields(head)
-
-	fmt.Println("optimized head")
-	fmt.Println(head.dump())
-	fmt.Println("===============")
-
+	/*
+		fmt.Println("optimized head")
+		fmt.Println(head.dump())
+		fmt.Println("===============")
+	*/
 	ret := (*opcode)(unsafe.Pointer(head))
 	compiled.code = ret
 
diff --git a/encode_vm.go b/encode_vm.go
index 8ffa0d4..49d4a9e 100644
--- a/encode_vm.go
+++ b/encode_vm.go
@@ -38,10 +38,10 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 	seenPtr := map[uintptr]struct{}{}
 	ptrOffset := uintptr(0)
 	ctxptr := ctx.ptr()
-	fmt.Println(code.dump())
+	//fmt.Println(code.dump())
 
 	for {
-		fmt.Printf("[%d]:[%s]\n", code.displayIdx, code.op)
+		//fmt.Printf("[%d]:[%s]\n", code.displayIdx, code.op)
 		switch code.op {
 		default:
 			return fmt.Errorf("failed to handle opcode. doesn't implement %s", code.op)
@@ -4195,7 +4195,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 				code = code.next
 			}
 		case opStructField:
-			if e.buf[len(e.buf)-1] != '{' {
+			if e.buf[len(e.buf)-1] != '{' && e.buf[len(e.buf)-1] != ',' {
 				e.encodeByte(',')
 			}
 			if !code.anonymousKey {
@@ -4218,7 +4218,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			}
 			code = code.next
 		case opStructFieldInt:
-			if e.buf[len(e.buf)-1] != '{' {
+			if e.buf[len(e.buf)-1] != '{' && e.buf[len(e.buf)-1] != ',' {
 				e.encodeByte(',')
 			}
 			ptr := load(ctxptr, code.headIdx)
@@ -5900,7 +5900,12 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			e.encodeString(*(*string)(unsafe.Pointer(&bytes)))
 			code = code.next
 		case opStructEnd:
-			e.encodeByte('}')
+			last := len(e.buf) - 1
+			if e.buf[last] == ',' {
+				e.buf[last] = '}'
+			} else {
+				e.encodeByte('}')
+			}
 			code = code.next
 		case opStructAnonymousEnd:
 			code = code.next
diff --git a/json.go b/json.go
index b25f191..e6922b7 100644
--- a/json.go
+++ b/json.go
@@ -317,6 +317,9 @@ func (n Number) Int64() (int64, error) {
 }
 
 func (n Number) MarshalJSON() ([]byte, error) {
+	if n == "" {
+		return []byte("0"), nil
+	}
 	if _, err := n.Float64(); err != nil {
 		return nil, err
 	}