diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index e8445db..4876e3d 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -1,4 +1,4 @@
-*filetype.txt*  For Vim version 9.1.  Last change: 2024 Jan 01
+*filetype.txt*	For Vim version 9.1.  Last change: 2024 Jan 04
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -148,6 +148,7 @@
 	*.cls		g:filetype_cls
 	*.csh		g:filetype_csh		|ft-csh-syntax|
 	*.dat		g:filetype_dat
+	*.def		g:filetype_def
 	*.f		g:filetype_f		|ft-forth-syntax|
 	*.frm		g:filetype_frm		|ft-form-syntax|
 	*.fs		g:filetype_fs		|ft-forth-syntax|
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index e3cac2e..cc293a5 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -2251,6 +2251,56 @@
 	let filetype_m = "mma"
 
 
+MODULA2					*modula2.vim* *ft-modula2-syntax*
+
+Vim will recognise comments with dialect tags to automatically select a given
+dialect.
+
+The syntax for a dialect tag comment is: >
+
+	taggedComment :=
+	  '(*!' dialectTag '*)'
+	  ;
+
+	dialectTag :=
+	  m2pim | m2iso | m2r10
+	  ;
+
+	reserved words
+	  m2pim = 'm2pim', m2iso = 'm2iso', m2r10 = 'm2r10'
+
+A dialect tag comment is recognised by Vim if it occurs within the first 200
+lines of the source file. Only the very first such comment is recognised, any
+additional dialect tag comments are ignored.
+
+Example: >
+
+	DEFINITION MODULE FooLib; (*!m2pim*)
+	...
+
+Variable g:modula2_default_dialect sets the default Modula-2 dialect when the
+dialect cannot be determined from the contents of the Modula-2 file: if
+defined and set to 'm2pim', the default dialect is PIM.
+
+Example: >
+
+	let g:modula2_default_dialect = 'm2pim'
+
+
+Highlighting is further configurable for each dialect via the following
+variables.
+
+Variable			Highlight ~
+*modula2_iso_allow_lowline*	allow low line in identifiers
+*modula2_iso_disallow_octals*	disallow octal integer literals
+*modula2_iso_disallow_synonyms*	disallow "@", "&" and "~" synonyms
+
+*modula2_pim_allow_lowline*	allow low line in identifiers
+*modula2_pim_disallow_octals*	disallow octal integer literals
+*modula2_pim_disallow_synonyms*	disallow "&" and "~" synonyms
+
+*modula2_r10_allow_lowline*	allow low line in identifiers
+
 MOO						*moo.vim* *ft-moo-syntax*
 
 If you use C-style comments inside expressions and find it mangles your
diff --git a/runtime/doc/tags b/runtime/doc/tags
index 9af1ac0..5b9e5a9 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -7270,6 +7270,7 @@
 ft-metapost-mappings	ft_mp.txt	/*ft-metapost-mappings*
 ft-metapost-settings	ft_mp.txt	/*ft-metapost-settings*
 ft-mma-syntax	syntax.txt	/*ft-mma-syntax*
+ft-modula2-syntax	syntax.txt	/*ft-modula2-syntax*
 ft-moo-syntax	syntax.txt	/*ft-moo-syntax*
 ft-msql-syntax	syntax.txt	/*ft-msql-syntax*
 ft-n1ql-syntax	syntax.txt	/*ft-n1ql-syntax*
@@ -8659,6 +8660,14 @@
 modeline-local	options.txt	/*modeline-local*
 modeline-version	options.txt	/*modeline-version*
 modifyOtherKeys	map.txt	/*modifyOtherKeys*
+modula2.vim	syntax.txt	/*modula2.vim*
+modula2_iso_allow_lowline	syntax.txt	/*modula2_iso_allow_lowline*
+modula2_iso_disallow_octals	syntax.txt	/*modula2_iso_disallow_octals*
+modula2_iso_disallow_synonyms	syntax.txt	/*modula2_iso_disallow_synonyms*
+modula2_pim_allow_lowline	syntax.txt	/*modula2_pim_allow_lowline*
+modula2_pim_disallow_octals	syntax.txt	/*modula2_pim_disallow_octals*
+modula2_pim_disallow_synonyms	syntax.txt	/*modula2_pim_disallow_synonyms*
+modula2_r10_allow_lowline	syntax.txt	/*modula2_r10_allow_lowline*
 moo.vim	syntax.txt	/*moo.vim*
 more-compatible	version5.txt	/*more-compatible*
 more-prompt	message.txt	/*more-prompt*