diff --git a/Doc/library/mmap.rst b/Doc/library/mmap.rst
index 33baf2bfae2..9652894c028 100644
--- a/Doc/library/mmap.rst
+++ b/Doc/library/mmap.rst
@@ -127,7 +127,7 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
       import mmap
 
       with mmap.mmap(-1, 13) as mm:
-          mm.write("Hello world!")
+          mm.write(b"Hello world!")
 
    .. versionadded:: 3.2
       Context manager support.