diff --git a/contrib/subtree/Makefile b/contrib/subtree/Makefile
index 8fe0bfd401..c0c9f21cb7 100644
--- a/contrib/subtree/Makefile
+++ b/contrib/subtree/Makefile
@@ -50,7 +50,7 @@ GIT_SUBTREE    := git-subtree
 
 GIT_SUBTREE_DOC := git-subtree.1
 GIT_SUBTREE_XML := git-subtree.xml
-GIT_SUBTREE_TXT := git-subtree.txt
+GIT_SUBTREE_TXT := git-subtree.adoc
 GIT_SUBTREE_HTML := git-subtree.html
 GIT_SUBTREE_TEST := ../../git-subtree
 
diff --git a/contrib/subtree/git-subtree.txt b/contrib/subtree/git-subtree.adoc
similarity index 100%
rename from contrib/subtree/git-subtree.txt
rename to contrib/subtree/git-subtree.adoc
diff --git a/contrib/subtree/meson.build b/contrib/subtree/meson.build
index a752a188df..9c72b23625 100644
--- a/contrib/subtree/meson.build
+++ b/contrib/subtree/meson.build
@@ -32,7 +32,7 @@ if get_option('docs').contains('man')
       '@INPUT@',
     ],
     depends: documentation_deps,
-    input: 'git-subtree.txt',
+    input: 'git-subtree.adoc',
     output: 'git-subtree.xml',
   )
 
@@ -63,7 +63,7 @@ if get_option('docs').contains('html')
       '@INPUT@',
     ],
     depends: documentation_deps,
-    input: 'git-subtree.txt',
+    input: 'git-subtree.adoc',
     output: 'git-subtree.html',
     install: true,
     install_dir: get_option('datadir') / 'doc/git-doc',