diff --git a/foo.h b/foo.h
index 2ca7dea..1246806 100644
--- a/foo.h
+++ b/foo.h
@@ -2,4 +2,4 @@
 
 #define bit_for_each64(pos, tmp, ul)  \
     for (tmp = ul, pos = ffs64(tmp); pos; tmp &= (tmp - 1),  pos = ffs64(tmp))
-
+#define true 1