diff --git a/src/lib_json/json_value.cpp b/src/lib_json/json_value.cpp
index 2690084..46385b9 100644
--- a/src/lib_json/json_value.cpp
+++ b/src/lib_json/json_value.cpp
@@ -52,9 +52,6 @@ const LargestInt Value::minLargestInt = LargestInt(~(LargestUInt(-1) / 2));
 const LargestInt Value::maxLargestInt = LargestInt(LargestUInt(-1) / 2);
 const LargestUInt Value::maxLargestUInt = LargestUInt(-1);
 
-/// Unknown size marker
-static const size_t unknown = (size_t)-1;
-
 #if !defined(JSON_USE_INT64_DOUBLE_CONVERSION)
 template <typename T, typename U>
 static inline bool InRange(double d, T min, U max) {
@@ -83,10 +80,7 @@ static inline bool InRange(double d, T min, U max) {
  * @return Pointer on the duplicate instance of string.
  */
 static inline char* duplicateStringValue(const char* value,
-                                         size_t length = unknown) {
-  if (length == unknown)
-    length = strlen(value);
-
+                                         size_t length) {
   // Avoid an integer overflow in the call to malloc below by limiting length
   // to a sane value.
   if (length >= (size_t)Value::maxInt)