diff --git a/os_dep.c b/os_dep.c
index c5f9e61be..ee6da3efd 100644
--- a/os_dep.c
+++ b/os_dep.c
@@ -2770,7 +2770,7 @@ block_unmap_inner(ptr_t start_addr, size_t len)
 #    ifdef SN_TARGET_PS3
     ps3_free_mem(start_addr, len);
 #    elif defined(AIX) || defined(COSMO) || defined(CYGWIN32) \
-        || defined(HPUX) || defined(SERENITY)                 \
+        || defined(HPUX)                                      \
         || (defined(LINUX) && !defined(PREFER_MMAP_PROT_NONE))
     /* On AIX, mmap(PROT_NONE) fails with ENOMEM unless the       */
     /* environment variable XPG_SUS_ENV is set to ON.             */