diff --git a/CHANGES.rst b/CHANGES.rst
index 6e8e5c6c..41b84850 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -3,7 +3,7 @@ Changelog
 
 6.1 (unreleased)
 ----------------
-
+- Improve performance of simple ``not`` queries on large catalogs.
 - Fix case where multiple indexes with similar name seperated by ``_`` were interpreted as options.
   (`#78 <https://github.com/zopefoundation/Products.ZCatalog/issues/78>`_)
 - Fix reversed sorting by multiple index by forcing the ``_sort_iterate_resultset``
diff --git a/src/Products/PluginIndexes/unindex.py b/src/Products/PluginIndexes/unindex.py
index 2b616271..9110bb0a 100644
--- a/src/Products/PluginIndexes/unindex.py
+++ b/src/Products/PluginIndexes/unindex.py
@@ -479,15 +479,6 @@ def query_index(self, record, resultset=None):
 
                     return cached
 
-        if not record.keys and not_parm:
-            # convert into indexed format
-            not_parm = list(map(self._convert, not_parm))
-            # we have only a 'not' query
-            record.keys = [k for k in index.keys() if k not in not_parm]
-        else:
-            # convert query arguments into indexed format
-            record.keys = list(map(self._convert, record.keys))
-
         # Range parameter
         range_parm = record.get('range', None)
         if range_parm:
@@ -503,6 +494,21 @@ def query_index(self, record, resultset=None):
             opr = record.usage.lower().split(':')
             opr, opr_args = opr[0], opr[1:]
 
+        # not query
+        if not record.keys and not_parm:
+            # convert into indexed format
+            not_parm = list(map(self._convert, not_parm))
+            # we have only a 'not' query
+            # shortcut/optimization if we have no 'opr' (i.e. no range)
+            if resultset is not None and opr is None:
+                i_not_parm = self._apply_not(not_parm, resultset)
+                if i_not_parm:
+                    return difference(resultset, i_not_parm)
+            record.keys = [k for k in index.keys() if k not in not_parm]
+        else:
+            # convert query arguments into indexed format
+            record.keys = list(map(self._convert, record.keys))
+
         if opr == 'range':  # range search
             if 'min' in opr_args:
                 lo = min(record.keys)