diff --git a/gc.h b/gc.h
index f63a618..72bef08 100644
--- a/gc.h
+++ b/gc.h
@@ -25,13 +25,13 @@ typedef intptr_t fixnum_t;
 
 /* Special values (0 <= n < 1024) */
 /* These correspond to objects within the first page of memory */
-#define SPECIAL_VALUE(n)  ((value_t)(4*n+2))
+#define SPECIAL_VALUE(n)  ((value_t)(4*(n)+2))
+#define TYPE_TAG(n)       SPECIAL_VALUE(768+(n))
 #define MAX_SPECIAL       SPECIAL_VALUE(1023)
 
 #define BROKEN_HEART      SPECIAL_VALUE(0)
 #define FALSE_VALUE       SPECIAL_VALUE(1)
 #define TRUE_VALUE        SPECIAL_VALUE(2)
-#define TYPE_TAG(n)       SPECIAL_VALUE(2+(n))
 
 #define TYPE_TAG_BOX      TYPE_TAG(0)
 #define TYPE_TAG_VECTOR   TYPE_TAG(1)