diff --git a/rts/include/Stg.h b/rts/include/Stg.h
index 1f7da9530c4157e1af711af25ad51812435c9b0f..1932236cf39d3f3b472856d81184ac6a0412837c 100644
--- a/rts/include/Stg.h
+++ b/rts/include/Stg.h
@@ -129,7 +129,7 @@
 
 /* Compute offsets of struct fields
  */
-#define STG_FIELD_OFFSET(s_type, field) ((StgWord)&(((s_type*)0)->field))
+#define STG_FIELD_OFFSET(s_type, field) __builtin_offsetof(s_type, field)
 
 /*
  * 'Portable' inlining: