--- a/tests/test-annotate.t	Thu May 03 12:10:47 2018 +0900
+++ b/tests/test-annotate.t	Thu May 03 12:04:36 2018 +0900
@@ -76,6 +76,11 @@
   $ hg annotate -T'{lines % "{rev} {node|shortest}: {line}"}' a
   0 8435: a
 
+'{line_number}' field should be populated as necessary
+
+  $ hg annotate -T'{lines % "{rev}:{line_number}: {line}"}' a
+  0:1: a
+
   $ cat <<EOF >>a
   > a
   > a