diff --git a/src/ripple/json/impl/json_reader.cpp b/src/ripple/json/impl/json_reader.cpp
index 13b9c5580d3..45b2794c779 100644
--- a/src/ripple/json/impl/json_reader.cpp
+++ b/src/ripple/json/impl/json_reader.cpp
@@ -29,6 +29,8 @@ namespace Json
 // Implementation of class Reader
 // ////////////////////////////////
 
+constexpr unsigned Reader::nest_limit;
+
 static
 std::string
 codePointToUTF8 (unsigned int cp)