diff --git a/src/json.c b/src/json.c
index c269f4f0..10e890a1 100644
--- a/src/json.c
+++ b/src/json.c
@@ -29,6 +29,8 @@
 
 #include "json.h"
 
+#define UNUSED(x)  ( (void) x )
+
 #ifdef _MSC_VER
    #ifndef _CRT_SECURE_NO_WARNINGS
       #define _CRT_SECURE_NO_WARNINGS
@@ -92,12 +94,14 @@ typedef struct
 
 static void * default_alloc (size_t size, int zero, void * user_data)
 {
-   return zero ? calloc (1, size) : malloc (size);
+    UNUSED(user_data);
+    return zero ? calloc (1, size) : malloc (size);
 }
 
 static void default_free (void * ptr, void * user_data)
 {
-   free (ptr);
+    UNUSED(user_data);
+    free (ptr);
 }
 
 static void * json_alloc (json_state * state, unsigned long size, int zero)