diff --git a/include/json.h b/include/json.h
index 6f9fec97c..7d840fa51 100644
--- a/include/json.h
+++ b/include/json.h
@@ -82,7 +82,7 @@ namespace crow
             Object,
         };
 
-        const char* get_type_str(type t) {
+        inline const char* get_type_str(type t) {
             switch(t){
                 case type::Number: return "Number";
                 case type::False: return "False";