diff --git a/CHANGES.rst b/CHANGES.rst
index 4d550d20..709d6af9 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,8 +4,10 @@ Changelog
 5.3 (unreleased)
 ----------------
 
-- Add support for Python 3.9.
+- Fix case where multiple indexes with similar name seperated by ``_`` were interpreted as options
+  (`#78 <https://github.com/zopefoundation/Products.ZCatalog/issues/78>`_).
 
+- Add support for Python 3.9.
 
 5.2 (2020-10-09)
 ----------------
diff --git a/src/Products/ZCatalog/query.py b/src/Products/ZCatalog/query.py
index 87a7309c..f7e5f949 100644
--- a/src/Products/ZCatalog/query.py
+++ b/src/Products/ZCatalog/query.py
@@ -88,8 +88,7 @@ def __init__(self, request, iid, options=(), operators=('or', 'and'),
 
             for field in request.keys():
                 if field.startswith(iid + '_'):
-                    iid_tmp, op = field.split('_')
-
+                    op = field[len(iid) + 1:]
                     self.set(op, request[field])
 
         self.keys = keys