diff --git a/libc/include/malloc.h b/libc/include/malloc.h
index aa046b9..ba0af3c 100644
--- a/libc/include/malloc.h
+++ b/libc/include/malloc.h
@@ -162,14 +162,14 @@
  *
  * Available since API level 27.
  */
-#define M_DECAY_TIME -100
+#define M_DECAY_TIME (-100)
 /**
  * mallopt() option to immediately purge any memory not in use. This
  * will release the memory back to the kernel. The value is ignored.
  *
  * Available since API level 28.
  */
-#define M_PURGE -101
+#define M_PURGE (-101)
 
 /**
  * [mallopt(3)](http://man7.org/linux/man-pages/man3/mallopt.3.html) modifies