diff --git a/qutebrowser/completion/models/histcategory.py b/qutebrowser/completion/models/histcategory.py
index 7db6ca902..57a2aa936 100644
--- a/qutebrowser/completion/models/histcategory.py
+++ b/qutebrowser/completion/models/histcategory.py
@@ -75,7 +75,7 @@ class HistoryCategory(QSqlQueryModel):
         # build a where clause to match all of the words in any order
         # given the search term "a b", the WHERE clause would be:
         # ((url || title) LIKE '%a%') AND ((url || title) LIKE '%b%')
-        wheres = ' AND '.join(
+        where_clause = ' AND '.join(
             "(url || title) LIKE :{} escape '\\'".format(i)
             for i in range(len(words)))
 
@@ -84,7 +84,7 @@ class HistoryCategory(QSqlQueryModel):
         timefmt = ("strftime('{}', last_atime, 'unixepoch', 'localtime')"
                    .format(timestamp_format.replace("'", "`")))
 
-        if not self._query or len(wheres) != len(self._query.boundValues()):
+        if not self._query or len(words) != len(self._query.boundValues()):
             # if the number of words changed, we need to generate a new query
             # otherwise, we can reuse the prepared query for performance
             self._query = sql.Query(' '.join([
@@ -92,7 +92,7 @@ class HistoryCategory(QSqlQueryModel):
                 "FROM CompletionHistory",
                 # the incoming pattern will have literal % and _ escaped
                 # we need to tell sql to treat '\' as an escape character
-                'WHERE ({})'.format(wheres),
+                'WHERE ({})'.format(where_clause),
                 self._atime_expr(),
                 "ORDER BY last_atime DESC",
             ]), forward_only=False)
diff --git a/tests/unit/completion/test_histcategory.py b/tests/unit/completion/test_histcategory.py
index 8458c3311..e42f9b91f 100644
--- a/tests/unit/completion/test_histcategory.py
+++ b/tests/unit/completion/test_histcategory.py
@@ -93,6 +93,38 @@ def test_set_pattern(pattern, before, after, model_validator, hist):
     model_validator.validate(after)
 
 
+def test_set_pattern_repeated(model_validator, hist):
+    """Validate multiple subsequent calls to set_pattern."""
+    hist.insert({'url': 'example.com/foo', 'title': 'title1', 'last_atime': 1})
+    hist.insert({'url': 'example.com/bar', 'title': 'title2', 'last_atime': 1})
+    hist.insert({'url': 'example.com/baz', 'title': 'title3', 'last_atime': 1})
+    cat = histcategory.HistoryCategory()
+    model_validator.set_model(cat)
+
+    cat.set_pattern('b')
+    model_validator.validate([
+        ('example.com/bar', 'title2'),
+        ('example.com/baz', 'title3'),
+    ])
+
+    cat.set_pattern('ba')
+    model_validator.validate([
+        ('example.com/bar', 'title2'),
+        ('example.com/baz', 'title3'),
+    ])
+
+    cat.set_pattern('ba ')
+    model_validator.validate([
+        ('example.com/bar', 'title2'),
+        ('example.com/baz', 'title3'),
+    ])
+
+    cat.set_pattern('ba z')
+    model_validator.validate([
+        ('example.com/baz', 'title3'),
+    ])
+
+
 @pytest.mark.parametrize('max_items, before, after', [
     (-1, [
         ('a', 'a', '2017-04-16'),