diff --git a/charset_normalizer/models.py b/charset_normalizer/models.py
index 23411dae..5faaf1db 100644
--- a/charset_normalizer/models.py
+++ b/charset_normalizer/models.py
@@ -231,7 +231,7 @@ def alphabets(self) -> List[str]:
             unicode_range(char) for char in str(self)
         ]  # type: List[Optional[str]]
         # filter and sort
-        self._unicode_ranges = sorted([r for r in detected_ranges if r])  # type: ignore
+        self._unicode_ranges = sorted({r for r in detected_ranges if r})  # type: ignore
         return self._unicode_ranges
 
     @property