diff --git a/changedetectionio/model/Watch.py b/changedetectionio/model/Watch.py
index 2fc82616b04..6fd5d2e7f65 100644
--- a/changedetectionio/model/Watch.py
+++ b/changedetectionio/model/Watch.py
@@ -352,7 +352,7 @@ def threshold_seconds(self):
     # Iterate over all history texts and see if something new exists
     # Always applying .strip() to start/end but optionally replace any other whitespace
     def lines_contain_something_unique_compared_to_history(self, lines: list, ignore_whitespace=False):
-        local_lines = []
+        local_lines = set([])
         if lines:
             if ignore_whitespace:
                 if isinstance(lines[0], str): # Can be either str or bytes depending on what was on the disk