diff --git a/src/calibre/ebooks/txt/input.py b/src/calibre/ebooks/txt/input.py
index 12f780913c..c7f9dbefd4 100644
--- a/src/calibre/ebooks/txt/input.py
+++ b/src/calibre/ebooks/txt/input.py
@@ -114,6 +114,7 @@ class TXTInput(InputFormatPlugin):
         if options.formatting_type == 'heuristic':
             setattr(options, 'enable_heuristics', True)
             setattr(options, 'unwrap_lines', False)
+            setattr(options, 'smarten_punctuation', True)
 
         # Reformat paragraphs to block formatting based on the detected type.
         # We don't check for block because the processor assumes block.