diff --git a/lib/core/agent.py b/lib/core/agent.py
index 310b46ad9..67222ccc2 100644
--- a/lib/core/agent.py
+++ b/lib/core/agent.py
@@ -187,12 +187,12 @@ class Agent(object):
 
             if origValue:
                 regex = r"(\A|\b)%s=%s%s" % (re.escape(parameter), re.escape(origValue), r"(\Z|\b)" if origValue[-1].isalnum() else "")
-                retVal = _(regex, "%s=%s" % (parameter, self.addPayloadDelimiters(newValue.replace("\\", "\\\\"))), paramString)
+                retVal = _(regex, "%s=%s" % (parameter, self.addPayloadDelimiters(newValue)), paramString)
             else:
-                retVal = _(r"(\A|\b)%s=%s(\Z|%s|%s|\s)" % (re.escape(parameter), re.escape(origValue), DEFAULT_GET_POST_DELIMITER, DEFAULT_COOKIE_DELIMITER), "%s=%s\g<2>" % (parameter, self.addPayloadDelimiters(newValue.replace("\\", "\\\\"))), paramString)
+                retVal = _(r"(\A|\b)%s=%s(\Z|%s|%s|\s)" % (re.escape(parameter), re.escape(origValue), DEFAULT_GET_POST_DELIMITER, DEFAULT_COOKIE_DELIMITER), "%s=%s\g<2>" % (parameter, self.addPayloadDelimiters(newValue)), paramString)
 
             if retVal == paramString and urlencode(parameter) != parameter:
-                retVal = _(r"(\A|\b)%s=%s" % (re.escape(urlencode(parameter)), re.escape(origValue)), "%s=%s" % (urlencode(parameter), self.addPayloadDelimiters(newValue.replace("\\", "\\\\"))), paramString)
+                retVal = _(r"(\A|\b)%s=%s" % (re.escape(urlencode(parameter)), re.escape(origValue)), "%s=%s" % (urlencode(parameter), self.addPayloadDelimiters(newValue)), paramString)
 
         if retVal:
             retVal = retVal.replace(BOUNDARY_BACKSLASH_MARKER, '\\')