diff --git a/micall/utils/find_maximum_overlap.py b/micall/utils/find_maximum_overlap.py
index c46fb33e0..f2748a010 100644
--- a/micall/utils/find_maximum_overlap.py
+++ b/micall/utils/find_maximum_overlap.py
@@ -7,6 +7,9 @@
 from itertools import chain
 
 
+# TODO: optimize the time complexity here. In particular, don't use
+# the slow `numpy.convolve`.
+
 def find_maximum_overlap(arr1: Sequence[object],
                          arr2: Sequence[object],
                          ) -> int: