diff --git a/thirdparty/json.lua b/thirdparty/json.lua
index 2e6e34f3..ddca7815 100644
--- a/thirdparty/json.lua
+++ b/thirdparty/json.lua
@@ -2,6 +2,9 @@ json = {}
 
 function json:include(includes)
 	if includes:handle(self:name()) then
+		defines {
+			"JSON_DIAGNOSTICS=1"
+		}
 		includedirs {
 			path.join(ThirdPartyFolder(), "json", "single_include")
 		}