--- a/src/testdir/test_spellfile.vim
+++ b/src/testdir/test_spellfile.vim
@@ -510,6 +510,207 @@ func Test_mkspell()
   call assert_fails('mkspell en en_US abc_xyz', 'E755:')
 endfunc
 
+" Tests for :mkspell with a .dic and .aff file
+func Test_aff_file_format_error()
+  " No word count in .dic file
+  call writefile([], 'Xtest.dic')
+  call writefile([], 'Xtest.aff')
+  call assert_fails('mkspell! Xtest.spl Xtest', 'E760:')
+
+  " Invalid encoding in .aff file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['# comment', 'SET Xinvalidencoding'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Conversion in Xtest.aff not supported: from xinvalidencoding', output)
+
+  " Invalid flag in .aff file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['FLAG xxx'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Invalid value for FLAG in Xtest.aff line 1: xxx', output)
+
+  " set FLAGS after using flag for an affix
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['SFX L Y 1', 'SFX L 0 re [^x]', 'FLAG long'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('FLAG after using flags in Xtest.aff line 3: long', output)
+
+  " INFO in affix file
+  let save_encoding = &encoding
+  call mkdir('Xrtp/spell', 'p')
+  call writefile(['1', 'work'], 'Xrtp/spell/Xtest.dic')
+  call writefile(['NAME klingon', 'VERSION 1.4', 'AUTHOR Spock'],
+        \ 'Xrtp/spell/Xtest.aff')
+  silent mkspell! Xrtp/spell/Xtest.utf-8.spl Xrtp/spell/Xtest
+  let save_rtp = &rtp
+  set runtimepath=./Xrtp
+  set spelllang=Xtest
+  set spell
+  let output = split(execute('spellinfo'), "\n")
+  call assert_equal("NAME klingon", output[1])
+  call assert_equal("VERSION 1.4", output[2])
+  call assert_equal("AUTHOR Spock", output[3])
+  let &rtp = save_rtp
+  call delete('Xrtp', 'rf')
+  set spell& spelllang& spellfile&
+  %bw!
+  " 'encoding' must be set again to clear the spell file in memory
+  let &encoding = save_encoding
+
+  " COMPOUNDFORBIDFLAG flag after PFX in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L 0 re x', 'COMPOUNDFLAG c', 'COMPOUNDFORBIDFLAG x'],
+        \ 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Defining COMPOUNDFORBIDFLAG after PFX item may give wrong results in Xtest.aff line 4', output)
+
+  " COMPOUNDPERMITFLAG flag after PFX in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L 0 re x', 'COMPOUNDPERMITFLAG c'],
+        \ 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Defining COMPOUNDPERMITFLAG after PFX item may give wrong results in Xtest.aff line 3', output)
+
+  " Wrong COMPOUNDRULES flag value in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['COMPOUNDRULES a'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Wrong COMPOUNDRULES value in Xtest.aff line 1: a', output)
+
+  " Wrong COMPOUNDWORDMAX flag value in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['COMPOUNDWORDMAX 0'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Wrong COMPOUNDWORDMAX value in Xtest.aff line 1: 0', output)
+
+  " Wrong COMPOUNDMIN flag value in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['COMPOUNDMIN 0'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Wrong COMPOUNDMIN value in Xtest.aff line 1: 0', output)
+
+  " Wrong COMPOUNDSYLMAX flag value in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['COMPOUNDSYLMAX 0'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Wrong COMPOUNDSYLMAX value in Xtest.aff line 1: 0', output)
+
+  " Wrong CHECKCOMPOUNDPATTERN flag value in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['CHECKCOMPOUNDPATTERN 0'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Wrong CHECKCOMPOUNDPATTERN value in Xtest.aff line 1: 0', output)
+
+  " Duplicate affix entry in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L 0 re x', 'PFX L Y 1', 'PFX L 0 re x'],
+        \ 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Duplicate affix in Xtest.aff line 3: L', output)
+
+  " Duplicate affix entry in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L Y 1'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Unrecognized or duplicate item in Xtest.aff line 2: PFX', output)
+
+  " Different combining flags in an affix file
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L 0 re x', 'PFX L N 1'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Different combining flag in continued affix block in Xtest.aff line 3', output)
+
+  " Try to reuse a affix used for BAD flag
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['BAD x', 'PFX x Y 1', 'PFX x 0 re x'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Affix also used for BAD/RARE/KEEPCASE/NEEDAFFIX/NEEDCOMPOUND/NOSUGGEST in Xtest.aff line 2: x', output)
+
+  " Trailing characters in an affix entry
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1 Test', 'PFX L 0 re x'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Trailing text in Xtest.aff line 1: Test', output)
+
+  " Trailing characters in an affix entry
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L Y 1', 'PFX L 0 re x Test'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Trailing text in Xtest.aff line 2: Test', output)
+
+  " Incorrect combine flag in an affix entry
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['PFX L X 1', 'PFX L 0 re x'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Expected Y or N in Xtest.aff line 1: X', output)
+
+  " Invalid count for REP item
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['REP a'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Expected REP(SAL) count in Xtest.aff line 1', output)
+
+  " Trailing characters in REP item
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['REP 1', 'REP f ph test'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Trailing text in Xtest.aff line 2: test', output)
+
+  " Invalid count for MAP item
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['MAP a'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Expected MAP count in Xtest.aff line 1', output)
+
+  " Duplicate character in a MAP item
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['MAP 2', 'MAP xx', 'MAP yy'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Duplicate character in MAP in Xtest.aff line 2', output)
+
+  " Use COMPOUNDSYLMAX without SYLLABLE
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['COMPOUNDSYLMAX 2'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('COMPOUNDSYLMAX used without SYLLABLE', output)
+
+  " Missing SOFOTO
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['SOFOFROM abcdef'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Missing SOFOTO line in Xtest.aff', output)
+
+  " FIXME: The following test causes a heap overflow with the ASAN build
+  " " Both SAL and SOFOFROM/SOFOTO items
+  " call writefile(['1', 'work'], 'Xtest.dic')
+  " call writefile(['SOFOFROM abcd', 'SOFOTO ABCD', 'SAL CIA X'], 'Xtest.aff')
+  " let output = execute('mkspell! Xtest.spl Xtest')
+  " call assert_match('Both SAL and SOFO lines in Xtest.aff', output)
+
+  " use an alphabet flag when FLAG is num
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['FLAG num', 'SFX L Y 1', 'SFX L 0 re [^x]'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Flag is not a number in Xtest.aff line 2: L', output)
+
+  " use number and alphabet flag when FLAG is num
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['FLAG num', 'SFX 4f Y 1', 'SFX 4f 0 re [^x]'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Affix name too long in Xtest.aff line 2: 4f', output)
+
+  " use a single character flag when FLAG is long
+  call writefile(['1', 'work'], 'Xtest.dic')
+  call writefile(['FLAG long', 'SFX L Y 1', 'SFX L 0 re [^x]'], 'Xtest.aff')
+  let output = execute('mkspell! Xtest.spl Xtest')
+  call assert_match('Illegal flag in Xtest.aff line 2: L', output)
+
+  call delete('Xtest.dic')
+  call delete('Xtest.aff')
+  call delete('Xtest.spl')
+  call delete('Xtest.sug')
+endfunc
+
 func Test_spell_add_word()
   set spellfile=
   call assert_fails('spellgood abc', 'E764:')
@@ -524,4 +725,26 @@ func Test_spell_add_word()
   %bw!
 endfunc
 
+" When 'spellfile' is not set, adding a new good word will automatically set
+" the 'spellfile'
+func Test_init_spellfile()
+  let save_rtp = &rtp
+  let save_encoding = &encoding
+  call mkdir('Xrtp/spell', 'p')
+  call writefile(['vim'], 'Xrtp/spell/Xtest.dic')
+  silent mkspell Xrtp/spell/Xtest.utf-8.spl Xrtp/spell/Xtest.dic
+  set runtimepath=./Xrtp
+  set spelllang=Xtest
+  set spell
+  silent spellgood abc
+  call assert_equal('./Xrtp/spell/Xtest.utf-8.add', &spellfile)
+  call assert_equal(['abc'], readfile('Xrtp/spell/Xtest.utf-8.add'))
+  call assert_true(filereadable('Xrtp/spell/Xtest.utf-8.spl'))
+  set spell& spelllang& spellfile&
+  call delete('Xrtp', 'rf')
+  let &encoding = save_encoding
+  let &rtp = save_rtp
+  %bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1522,
+/**/
     1521,
 /**/
     1520,