diff --git a/Modules/main.c b/Modules/main.c
index d36db6d8b511af..54e29008895808 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -68,9 +68,9 @@ static char *usage_2 = "\
 -S     : don't imply 'import site' on initialization\n\
 ";
 static char *usage_3 = "\
--u     : unbuffered binary stdout and stderr, stdin always buffered;\n\
+-u     : force the binary I/O layers of stdout and stderr to be unbuffered;\n\
+         stdin is always buffered; text I/O layer will be line-buffered;\n\
          also PYTHONUNBUFFERED=x\n\
-         see man page for details on internal buffering relating to '-u'\n\
 -v     : verbose (trace import statements); also PYTHONVERBOSE=x\n\
          can be supplied multiple times to increase verbosity\n\
 -V     : print the Python version number and exit (also --version)\n\