diff --git a/docs/manual/customize-outside-br.txt b/docs/manual/customize-outside-br.txt
index 110984308f..5d63e60bdf 100644
--- a/docs/manual/customize-outside-br.txt
+++ b/docs/manual/customize-outside-br.txt
@@ -1,4 +1,5 @@
 // -*- mode:doc -*- ;
+// vim: set syntax=asciidoc:
 
 [[outside-br-custom]]
 === Keeping customizations outside of Buildroot
diff --git a/docs/manual/customize-patches.txt b/docs/manual/customize-patches.txt
index a052915dfd..e129a64855 100644
--- a/docs/manual/customize-patches.txt
+++ b/docs/manual/customize-patches.txt
@@ -1,4 +1,5 @@
 // -*- mode:doc -*- ;
+// vim: set syntax=asciidoc:
 
 [[customize-patches]]
 === Adding project-specific patches
diff --git a/docs/manual/makeusers-syntax.txt b/docs/manual/makeusers-syntax.txt
index ecf3eb040a..ffdb961871 100644
--- a/docs/manual/makeusers-syntax.txt
+++ b/docs/manual/makeusers-syntax.txt
@@ -1,4 +1,5 @@
 // -*- mode:doc -*- ;
+// vim: set syntax=asciidoc:
 
 [[makeuser-syntax]]
 == Makeusers syntax documentation