diff --git a/libc/bionic/mmap.cpp b/libc/bionic/mmap.cpp
index febc459fa..75bea588f 100644
--- a/libc/bionic/mmap.cpp
+++ b/libc/bionic/mmap.cpp
@@ -37,13 +37,13 @@ extern "C" void*  __mmap2(void*, size_t, int, int, int, size_t);
 
 #define MMAP2_SHIFT 12 // 2**12 == 4096
 
-void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
+void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) {
   if (offset & ((1UL << MMAP2_SHIFT)-1)) {
     errno = EINVAL;
     return MAP_FAILED;
   }
 
-  size_t unsigned_offset = static_cast<size_t>(offset); // To avoid sign extension.
+  uint64_t unsigned_offset = static_cast<uint64_t>(offset); // To avoid sign extension.
   void* result = __mmap2(addr, size, prot, flags, fd, unsigned_offset >> MMAP2_SHIFT);
 
   if (result != MAP_FAILED && (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) != 0) {
@@ -53,3 +53,7 @@ void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
 
   return result;
 }
+
+void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
+  return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset));
+}
diff --git a/libc/include/sys/mman.h b/libc/include/sys/mman.h
index 7a3297430..7c5f8d774 100644
--- a/libc/include/sys/mman.h
+++ b/libc/include/sys/mman.h
@@ -45,6 +45,7 @@ __BEGIN_DECLS
 #define MREMAP_FIXED    2
 
 extern void*  mmap(void *, size_t, int, int, int, off_t);
+extern void*  mmap64(void *, size_t, int, int, int, off64_t);
 extern int    munmap(void *, size_t);
 extern int    msync(const void *, size_t, int);
 extern int    mprotect(const void *, size_t, int);