diff --git a/Scripts/EnumUtil.cs b/Scripts/EnumUtil.cs
index ce8e95b3f..556fa269d 100644
--- a/Scripts/EnumUtil.cs
+++ b/Scripts/EnumUtil.cs
@@ -5,15 +5,15 @@ namespace VRM
 {
     public static class EnumUtil
     {
-        public static T TryParseOrDefault<T>(string src)where T: struct
+        public static T TryParseOrDefault<T>(string src, T defaultValue=default(T)) where T : struct
         {
             try
             {
                 return (T)Enum.Parse(typeof(T), src, true);
             }
-            catch(Exception)
+            catch (Exception)
             {
-                return default(T);
+                return defaultValue;
             }
         }
     }
diff --git a/Scripts/Format/glTF_VRM_Humanoid.cs b/Scripts/Format/glTF_VRM_Humanoid.cs
index f9510cc51..08b03e471 100644
--- a/Scripts/Format/glTF_VRM_Humanoid.cs
+++ b/Scripts/Format/glTF_VRM_Humanoid.cs
@@ -65,28 +65,25 @@ namespace VRM
         rightLittleIntermediate,
         rightLittleDistal,
         upperChest,
+
+        unknown,
     }
 
     public static class VRMBoneExtensions
     {
         public static VRMBone FromHumanBodyBone(this HumanBodyBones human)
         {
-            return EnumUtil.TryParseOrDefault<VRMBone>(human.ToString());
+            return EnumUtil.TryParseOrDefault<VRMBone>(human.ToString(), VRMBone.unknown);
         }
         public static HumanBodyBones ToHumanBodyBone(this VRMBone bone)
         {
 #if  UNITY_5_6_OR_NEWER
-            return EnumUtil.TryParseOrDefault<HumanBodyBones>(bone.ToString());
-#else
             if (bone == VRMBone.upperChest)
             {
                 return HumanBodyBones.LastBone;
             }
-            else
-            {
-                return EnumUtil.TryParseOrDefault<HumanBodyBones>(bone.ToString());
-            }
 #endif
+            return EnumUtil.TryParseOrDefault<HumanBodyBones>(bone.ToString(), HumanBodyBones.LastBone);
         }
     }