1 files changed, 8 insertions, 1 deletions
diff --git a/Lib/email/policy.py b/Lib/email/policy.py
index 611deb5..8816c84 100644
--- a/Lib/email/policy.py
+++ b/Lib/email/policy.py
@@ -210,8 +210,15 @@ class EmailPolicy(Policy):
                   self.refold_source == 'long' and
                     (lines and len(lines[0])+len(name)+2 > maxlen or
                      any(len(x) > maxlen for x in lines[1:])))
-        if refold or refold_binary and _has_surrogates(value):
+
+        if not refold:
+            if not self.utf8:
+                refold = not value.isascii()
+            elif refold_binary:
+                refold = _has_surrogates(value)
+        if refold:
             return self.header_factory(name, ''.join(lines)).fold(policy=self)
+
         return name + ': ' + self.linesep.join(lines) + self.linesep