diff --git a/mypy.ini b/mypy.ini
index 2efd6b99..da81307c 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -20,4 +20,5 @@ warn_unused_ignores = True
 ignore_missing_imports = True
 
 [mypy-shapely.*]
+# https://github.com/Toblerity/Shapely/issues/721
 ignore_missing_imports = True
\ No newline at end of file