diff --git a/libc/bionic/mmap.cpp b/libc/bionic/mmap.cpp
index 57a8cdf..3503319 100644
--- a/libc/bionic/mmap.cpp
+++ b/libc/bionic/mmap.cpp
@@ -48,7 +48,7 @@
   }
 
   // prevent allocations large enough for `end - start` to overflow
-  size_t rounded = BIONIC_ALIGN(size, PAGE_SIZE);
+  size_t rounded = __BIONIC_ALIGN(size, PAGE_SIZE);
   if (rounded < size || rounded > PTRDIFF_MAX) {
     errno = ENOMEM;
     return MAP_FAILED;