diff --git a/SConstruct b/SConstruct
index 309d935c3..561ead5ab 100644
--- a/SConstruct
+++ b/SConstruct
@@ -1857,12 +1857,11 @@ help:always wipe certain freed memory
 		context.Message('%s: checking %s...' % (self.msgprefix, 'whether to use overwrite poisoning'))
 		r = 'overwrite' in self.user_settings.poison
 		context.Result(r)
-		if r:
-			context.sconf.Define('DXX_HAVE_POISON_OVERWRITE')
+		self._define_macro(context, 'DXX_HAVE_POISON_OVERWRITE', int(r))
 		return r
 	@_custom_test
 	def _check_poison_method(self,context,
-		_methods=(check_poison_valgrind, check_poison_overwrite),
+		_methods=(check_poison_overwrite, check_poison_valgrind),
 		poison = None
 	):
 		# Always run both checks.  The user may want a program that
diff --git a/common/include/poison.h b/common/include/poison.h
index e26c1ceae..0a2a7b5e4 100644
--- a/common/include/poison.h
+++ b/common/include/poison.h
@@ -32,10 +32,7 @@ template <typename T, typename V>
 static inline void _DXX_POISON_MEMORY_RANGE(T b, T e, const V &v)
 {
 #if DXX_HAVE_POISON
-	int store = 0;
-#ifdef DXX_HAVE_POISON_OVERWRITE
-	store |= 1;
-#endif
+	int store = DXX_HAVE_POISON_OVERWRITE;
 #ifdef DXX_HAVE_POISON_VALGRIND
 	if (!store)
 		store |= RUNNING_ON_VALGRIND;