diff --git a/libc/bionic/mmap.c b/libc/bionic/mmap.c
index 40a6538..e097086 100644
--- a/libc/bionic/mmap.c
+++ b/libc/bionic/mmap.c
@@ -34,10 +34,17 @@
 #define  MMAP2_SHIFT  12
 void* mmap(void *addr, size_t size, int prot, int flags, int fd, long offset)
 {
+    void *ret;
+
     if (offset & ((1UL << MMAP2_SHIFT)-1)) {
         errno = EINVAL;
         return MAP_FAILED;
     }
 
-    return __mmap2(addr, size, prot, flags, fd, (size_t)offset >> MMAP2_SHIFT);
+    ret = __mmap2(addr, size, prot, flags, fd, (size_t)offset >> MMAP2_SHIFT);
+
+    if (ret && (flags & (MAP_PRIVATE | MAP_ANONYMOUS)))
+	    madvise(ret, size, MADV_MERGEABLE);
+
+    return ret;
 }