diff --git a/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs b/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
index 835a2f35bb..0ce5833600 100644
--- a/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
+++ b/src/Microsoft.Net.Http.Headers/HttpRuleParser.cs
@@ -10,7 +10,7 @@ namespace Microsoft.Net.Http.Headers
 {
     internal static class HttpRuleParser
     {
-        private static readonly bool[] TokenChars;
+        private static readonly bool[] TokenChars = CreateTokenChars();
         private const int MaxNestedCount = 5;
         private static readonly string[] DateFormats = new string[] {
             // "r", // RFC 1123, required output format but too strict for input
@@ -43,36 +43,38 @@ namespace Microsoft.Net.Http.Headers
         // iso-8859-1, Western European (ISO)
         internal static readonly Encoding DefaultHttpEncoding = Encoding.GetEncoding("iso-8859-1");
 
-        static HttpRuleParser()
+        private static bool[] CreateTokenChars()
         {
             // token = 1*<any CHAR except CTLs or separators>
             // CTL = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
 
-            TokenChars = new bool[128]; // everything is false
+            var tokenChars = new bool[128]; // everything is false
 
             for (int i = 33; i < 127; i++) // skip Space (32) & DEL (127)
             {
-                TokenChars[i] = true;
+                tokenChars[i] = true;
             }
 
             // remove separators: these are not valid token characters
-            TokenChars[(byte)'('] = false;
-            TokenChars[(byte)')'] = false;
-            TokenChars[(byte)'<'] = false;
-            TokenChars[(byte)'>'] = false;
-            TokenChars[(byte)'@'] = false;
-            TokenChars[(byte)','] = false;
-            TokenChars[(byte)';'] = false;
-            TokenChars[(byte)':'] = false;
-            TokenChars[(byte)'\\'] = false;
-            TokenChars[(byte)'"'] = false;
-            TokenChars[(byte)'/'] = false;
-            TokenChars[(byte)'['] = false;
-            TokenChars[(byte)']'] = false;
-            TokenChars[(byte)'?'] = false;
-            TokenChars[(byte)'='] = false;
-            TokenChars[(byte)'{'] = false;
-            TokenChars[(byte)'}'] = false;
+            tokenChars[(byte)'('] = false;
+            tokenChars[(byte)')'] = false;
+            tokenChars[(byte)'<'] = false;
+            tokenChars[(byte)'>'] = false;
+            tokenChars[(byte)'@'] = false;
+            tokenChars[(byte)','] = false;
+            tokenChars[(byte)';'] = false;
+            tokenChars[(byte)':'] = false;
+            tokenChars[(byte)'\\'] = false;
+            tokenChars[(byte)'"'] = false;
+            tokenChars[(byte)'/'] = false;
+            tokenChars[(byte)'['] = false;
+            tokenChars[(byte)']'] = false;
+            tokenChars[(byte)'?'] = false;
+            tokenChars[(byte)'='] = false;
+            tokenChars[(byte)'{'] = false;
+            tokenChars[(byte)'}'] = false;
+
+            return tokenChars;
         }
 
         internal static bool IsTokenChar(char character)