diff --git a/src/Makefile b/src/Makefile
index 0d8f150..59511d2 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2338,7 +2338,8 @@
 # Also install most of the other runtime files.
 installrtbase: $(HELPSOURCE)/vim.1 $(DEST_VIM) $(VIMTARGET) $(DEST_RT) \
 		$(DEST_HELP) $(DEST_PRINT) $(DEST_COL) \
-		$(DEST_SYN) $(DEST_SYN)/shared $(DEST_IND) $(DEST_FTP) \
+		$(DEST_SYN) $(DEST_SYN)/modula2 $(DEST_SYN)/modula2/opt $(DEST_SYN)/shared \
+		$(DEST_IND) $(DEST_FTP) \
 		$(DEST_AUTO) $(DEST_AUTO)/dist $(DEST_AUTO)/xml $(DEST_AUTO)/zig \
 		$(DEST_IMPORT) $(DEST_IMPORT)/dist \
 		$(DEST_PLUG) $(DEST_TUTOR) $(DEST_SPELL) $(DEST_COMP)
@@ -2413,6 +2414,8 @@
 	cd $(DEST_SYN); chmod $(HELPMOD) *.vim README.txt
 	cd $(SYNSOURCE)/shared; $(INSTALL_DATA) *.vim README.txt $(DEST_SYN)/shared
 	cd $(DEST_SYN)/shared; chmod $(HELPMOD) *.vim README.txt
+	cd $(SYNSOURCE)/modula2/opt; $(INSTALL_DATA) *.vim $(DEST_SYN)/modula2/opt
+	cd $(DEST_SYN)/modula2/opt; chmod $(HELPMOD) *.vim
 # install the indent files
 	cd $(INDSOURCE); $(INSTALL_DATA) *.vim README.txt $(DEST_IND)
 	cd $(DEST_IND); chmod $(HELPMOD) *.vim README.txt
@@ -2661,6 +2664,7 @@
 $(DESTDIR)$(exec_prefix) $(DEST_BIN) \
 		$(DEST_VIM) $(DEST_RT) $(DEST_HELP) \
 		$(DEST_PRINT) $(DEST_COL) $(DEST_SYN) $(DEST_SYN)/shared \
+		$(DEST_SYN)/modula2 $(DEST_SYN)/modula2/opt \
 		$(DEST_IND) $(DEST_FTP) \
 		$(DEST_LANG) $(DEST_KMAP) $(DEST_COMP) $(DEST_MACRO) \
 		$(DEST_PACK) $(DEST_TOOLS) $(DEST_TUTOR) $(DEST_SPELL) \
@@ -2838,6 +2842,7 @@
 	-rm -rf $(DEST_COL)/tools
 	-rm -rf $(DEST_COL)/lists
 	-rm -f $(DEST_SYN)/shared/*.vim $(DEST_SYN)/shared/README.txt
+	-rm -f $(DEST_SYN)/modula2/opt/*.vim
 	-rm -f $(DEST_SYN)/*.vim $(DEST_SYN)/README.txt
 	-rm -f $(DEST_IND)/*.vim $(DEST_IND)/README.txt
 	-rm -rf $(DEST_MACRO)
@@ -2850,6 +2855,7 @@
 	-rm -rf $(DEST_COMP)
 	-rm -f $(DEST_PRINT)/*.ps
 	-rmdir $(DEST_HELP) $(DEST_PRINT) $(DEST_COL) $(DEST_SYN)/shared
+	-rmdir $(DEST_SYN)/modula2/opt $(DEST_SYN)/modula2
 	-rmdir $(DEST_SYN) $(DEST_IND)
 	-rm -rf $(DEST_FTP)/*.vim $(DEST_FTP)/README.txt $(DEST_FTP)/logtalk.dict
 	-rm -f $(DEST_AUTO)/*.vim $(DEST_AUTO)/README.txt
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index fe22069..6913eec 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -453,7 +453,6 @@
     mma: ['file.nb'],
     mmp: ['file.mmp'],
     modconf: ['/etc/modules.conf', '/etc/modules', '/etc/conf.modules', '/etc/modprobe.file', 'any/etc/conf.modules', 'any/etc/modprobe.file', 'any/etc/modules', 'any/etc/modules.conf'],
-    modula2: ['file.m2', 'file.mi'],
     modula3: ['file.m3', 'file.mg', 'file.i3', 'file.ig', 'file.lm3'],
     monk: ['file.isc', 'file.monk', 'file.ssc', 'file.tsc'],
     moo: ['file.moo'],
@@ -1642,13 +1641,16 @@
   call writefile(['IMPLEMENTATION MODULE Module2Mod;'], 'modfile.MOD')
   split modfile.MOD
   call assert_equal('modula2', &filetype)
+  call assert_equal('pim', b:modula2.dialect)
   bwipe!
 
   " Modula-2 with comment and empty lines prior MODULE
   call writefile(['', '(* with',  ' comment *)', '', 'MODULE Module2Mod;'], 'modfile.MOD')
   split modfile.MOD
   call assert_equal('modula2', &filetype)
+  call assert_equal('pim', b:modula2.dialect)
   bwipe!
+
   call delete('modfile.MOD')
 
   " LambdaProlog module
@@ -2376,4 +2378,38 @@
   filetype off
 endfunc
 
+func Test_def_file()
+  filetype on
+
+  call writefile(['this is the fallback'], 'Xfile.def', 'D')
+  split Xfile.def
+  call assert_equal('def', &filetype)
+  bwipe!
+
+  " Test dist#ft#FTdef()
+
+  let g:filetype_def = 'modula2'
+  split Xfile.def
+  call assert_equal('modula2', &filetype)
+  call assert_equal('pim', b:modula2.dialect)
+  bwipe!
+  unlet g:filetype_def
+
+  " Modula-2
+
+  call writefile(['(* a Modula-2 comment *)'], 'Xfile.def')
+  split Xfile.def
+  call assert_equal('modula2', &filetype)
+  call assert_equal('pim', b:modula2.dialect)
+  bwipe!
+
+  call writefile(['IMPLEMENTATION MODULE Module2Mod;'], 'Xfile.def')
+  split Xfile.def
+  call assert_equal('modula2', &filetype)
+  call assert_equal('pim', b:modula2.dialect)
+  bwipe!
+
+  filetype off
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 35865d6..8f6446f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    13,
+/**/
     12,
 /**/
     11,