diff --git a/src/calibre/gui2/tweak_book/spell.py b/src/calibre/gui2/tweak_book/spell.py
index 37dc5e3c6b..c074695999 100644
--- a/src/calibre/gui2/tweak_book/spell.py
+++ b/src/calibre/gui2/tweak_book/spell.py
@@ -1094,7 +1094,11 @@ class SpellCheck(Dialog):
             suggestions = dictionaries.suggestions(*w)
             self.suggested_list.clear()
             word_suggested = False
+            seen = set()
             for i, s in enumerate(chain(suggestions, (current_word,))):
+                if s in seen:
+                    continue
+                seen.add(s)
                 item = QListWidgetItem(s, self.suggested_list)
                 if i == 0:
                     self.suggested_list.setCurrentItem(item)