diff --git a/ctl/strcat.cc b/ctl/strcat.cc
index 58cbd74b6..05ba5a05e 100644
--- a/ctl/strcat.cc
+++ b/ctl/strcat.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/ctl/strcmp.cc b/ctl/strcmp.cc
index 0191c96cb..3503c5927 100644
--- a/ctl/strcmp.cc
+++ b/ctl/strcmp.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/ctl/string.cc b/ctl/string.cc
index 50899435c..9002113c1 100644
--- a/ctl/string.cc
+++ b/ctl/string.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/ctl/string_view.cc b/ctl/string_view.cc
index 61512d4d9..e8fb42b47 100644
--- a/ctl/string_view.cc
+++ b/ctl/string_view.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/test/ctl/optional_test.cc b/test/ctl/optional_test.cc
index 932cdf45d..de75ebe30 100644
--- a/test/ctl/optional_test.cc
+++ b/test/ctl/optional_test.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/test/ctl/string_test.cc b/test/ctl/string_test.cc
index 7d8a5fa6a..218b1b5ef 100644
--- a/test/ctl/string_test.cc
+++ b/test/ctl/string_test.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/test/ctl/string_view_test.cc b/test/ctl/string_view_test.cc
index aa73449a3..fb43d5898 100644
--- a/test/ctl/string_view_test.cc
+++ b/test/ctl/string_view_test.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //
diff --git a/test/ctl/vector_test.cc b/test/ctl/vector_test.cc
index 6636ec702..01d2301f7 100644
--- a/test/ctl/vector_test.cc
+++ b/test/ctl/vector_test.cc
@@ -1,5 +1,5 @@
 // -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
-// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 //
 // Copyright 2024 Justine Alexandra Roberts Tunney
 //