diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 7ffb3842..c6359e2b 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -65,7 +65,11 @@ static ID id_eq;
 static ID id_half;
 
 /* MACRO's to guard objects from GC by keeping them in stack */
+#ifdef RBIMPL_ATTR_MAYBE_UNUSED
+#define ENTER(n) RBIMPL_ATTR_MAYBE_UNUSED() volatile VALUE vStack[n];int iStack=0
+#else
 #define ENTER(n) volatile VALUE RB_UNUSED_VAR(vStack[n]);int iStack=0
+#endif
 #define PUSH(x)  (vStack[iStack++] = (VALUE)(x))
 #define SAVE(p)  PUSH((p)->obj)
 #define GUARD_OBJ(p,y) ((p)=(y), SAVE(p))