Finish bug fix applied at 58398. I missed a piece, Tal Einat found the error.
diff --git a/Lib/idlelib/IOBinding.py b/Lib/idlelib/IOBinding.py
index 6ab4db0..b970dba 100644
--- a/Lib/idlelib/IOBinding.py
+++ b/Lib/idlelib/IOBinding.py
@@ -392,7 +392,7 @@
         text = self.text.get("1.0", "end-1c")
         if self.eol_convention != "\n":
             text = text.replace("\n", self.eol_convention)
-        chars = self.encode(self.text.get("1.0", "end-1c"))
+        chars = self.encode(text)
         try:
             f = open(filename, "wb")
             f.write(chars)