diff --git a/Lib/poplib.py b/Lib/poplib.py
index ead661f..4e2c03b 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -28,8 +28,8 @@
 POP3_SSL_PORT = 995
 
 # Line terminators (we always output CRLF, but accept any of CRLF, LFCR, LF)
-CR = '\r'
-LF = '\n'
+CR = b'\r'
+LF = b'\n'
 CRLF = CR+LF