diff --git a/lib/http-proxy/common.js b/lib/http-proxy/common.js
index c00994cde..8fae2cd25 100644
--- a/lib/http-proxy/common.js
+++ b/lib/http-proxy/common.js
@@ -220,7 +220,7 @@ common.rewriteCookieProperty = function rewriteCookieProperty(header, config, pr
       return rewriteCookieProperty(headerElement, config, property);
     });
   }
-  return header.replace(new RegExp("(;\\s*" + property + "=)([^;]+)"), function(match, prefix, previousValue) {
+  return header.replace(new RegExp("(;\\s*" + property + "=)([^;]+)", 'i'), function(match, prefix, previousValue) {
     var newValue;
     if (previousValue in config) {
       newValue = config[previousValue];