diff --git a/Json5/Json5.cs b/Json5/Json5.cs
index df588b5..5bfb46c 100644
--- a/Json5/Json5.cs
+++ b/Json5/Json5.cs
@@ -157,16 +157,23 @@ private static string EscapeChar(char c, char quote)
 
             switch (c)
             {
+                case '\0': return "\\0";
                 case '\b': return "\\b";
                 case '\t': return "\\t";
                 case '\n': return "\\n";
                 case '\f': return "\\f";
                 case '\r': return "\\r";
+                case '\v': return "\\v";
                 case '\\': return "\\\\";
                 case '\u2028': return "\\u2028";
                 case '\u2029': return "\\u2029";
             }
 
+            if (c < ' ')
+            {
+                return "\\x" + ((int)c).ToString("x2");
+            }
+
             switch (char.GetUnicodeCategory(c))
             {
                 case UnicodeCategory.Control:
@@ -176,11 +183,7 @@ private static string EscapeChar(char c, char quote)
                 case UnicodeCategory.OtherNotAssigned:
                     return "\\u" + ((int)c).ToString("x4");
             }
-
-            // // Node does this.
-            //if(c <= 31)
-            //  return "\\u" + ((int)c).ToString("x4");
-
+            
             return c.ToString();
         }
     }
diff --git a/Json5/Json5Object.cs b/Json5/Json5Object.cs
index 36ac71b..422eaf9 100644
--- a/Json5/Json5Object.cs
+++ b/Json5/Json5Object.cs
@@ -3,6 +3,7 @@
 namespace Json5
 {
     using Parsing;
+    using System.Text.RegularExpressions;
 
     public class Json5Object : Json5Container, IEnumerable<KeyValuePair<string, Json5Value>>
     {
@@ -105,25 +106,18 @@ internal override string ToJson5String(string space, string indent, bool useOneS
             return s;
         }
 
+        // https://www.ecma-international.org/ecma-262/5.1/
+        // Match IdentifierName (except escapes)
+        private static Regex identifierNameRegex = new Regex(@"
+            ^
+                [\$_\p{L}\p{Nl}]
+                [\$_\p{L}\p{Nl}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\u200c\u200d]*
+            $
+        ", RegexOptions.IgnorePatternWhitespace | RegexOptions.Compiled);
+
         private string KeyToString(string key)
         {
-            if (key.Length == 0)
-                return "''";
-
-
-            // TODO: Create a Utility class for interally used methods.
-
-            //if(char.IsLetter(key[0]) || char.GetUnicodeCategory(key[0]) == System.Globalization.UnicodeCategory.LetterNumber)
-            //{
-            //  for(int i = 1; i < key.Length; i++)
-            //  {
-
-            //  }
-            //}
-
-            // This will not always work unless we check for Eof after the Identifier.
-            // We should probably handle this another way.
-            if (new Json5Lexer(key).Read().Type == Json5TokenType.Identifier)
+            if (identifierNameRegex.IsMatch(key))
                 return key;
 
             return Json5.QuoteString(key);