diff --git a/Lib/smtplib.py b/Lib/smtplib.py
index 75093ae0fa6..c1b1beca407 100755
--- a/Lib/smtplib.py
+++ b/Lib/smtplib.py
@@ -175,6 +175,7 @@ else:
             chr = None
             while chr != "\n":
                 chr = self.sslobj.read(1)
+                if not chr: break
                 str += chr
             return str