diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index f0939e6..e8773d9 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2133,8 +2133,18 @@
 	Commas can be added for readability.
 	To avoid problems with flags that are added in the future, use the
 	"+=" and "-=" feature of ":set" |add-option-flags|.
+
 	NOTE: This option is set to the Vi default value when 'compatible' is
 	set and to the Vim default value when 'compatible' is reset.
+
+	NOTE: In a |Vim9| script, when `vim9script` is encountered, the value
+	is saved, 'cpoptions' is set to the Vim default, and the saved value
+	is restored at the end of the script.  Changes to the value of
+	'cpoptions' will be applied to the saved value, but keep in mind that
+	removing a flag that is not present when 'cpoptions' is changed has no
+	effect.  In the |.vimrc| file the value is not restored, thus using
+	`vim9script` in the |.vimrc| file results in using the Vim default.
+
 	NOTE: This option is set to the POSIX default value at startup when
 	the Vi default value would be used and the $VIM_POSIX environment
 	variable exists |posix|.  This means Vim tries to behave like the
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 6c142a4..ced0c7d 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1402,6 +1402,7 @@
 The original value of 'cpoptions' is restored at the end of the script, while
 flags added or removed in the script are also added to or removed from the
 original value to get the same effect.  The order of flags may change.
+In the |vimrc| file sourced on startup this does not happen.
 
 							*vim9-mix*
 There is one way to use both legacy and Vim9 syntax in one script file: >
diff --git a/src/scriptfile.c b/src/scriptfile.c
index 7ff9672..129d4d6 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1372,6 +1372,9 @@
 	if (ret_sid != NULL)
 	    *ret_sid = current_sctx.sc_sid;
 
+	// Remember the "is_vimrc" flag for when the file is sourced again.
+	si->sn_is_vimrc = is_vimrc;
+
 	// Used to check script variable index is still valid.
 	si->sn_script_seq = current_sctx.sc_seq;
     }
@@ -1471,9 +1474,11 @@
 
 #ifdef FEAT_EVAL
 almosttheend:
+    // If "sn_save_cpo" is set that means we encountered "vim9script": restore
+    // 'cpoptions', unless in the main .vimrc file.
     // Get "si" again, "script_items" may have been reallocated.
     si = SCRIPT_ITEM(current_sctx.sc_sid);
-    if (si->sn_save_cpo != NULL)
+    if (si->sn_save_cpo != NULL && si->sn_is_vimrc == DOSO_NONE)
     {
 	if (STRCMP(p_cpo, CPO_VIM) != 0)
 	{
@@ -1503,8 +1508,8 @@
 		}
 	}
 	set_option_value((char_u *)"cpo", 0L, si->sn_save_cpo, OPT_NO_REDRAW);
-	VIM_CLEAR(si->sn_save_cpo);
     }
+    VIM_CLEAR(si->sn_save_cpo);
 
     restore_funccal();
 # ifdef FEAT_PROFILE
diff --git a/src/structs.h b/src/structs.h
index 4160453..4e770f1 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1866,6 +1866,7 @@
     int		sn_version;	// :scriptversion
     int		sn_state;	// SN_STATE_ values
     char_u	*sn_save_cpo;	// 'cpo' value when :vim9script found
+    char	sn_is_vimrc;	// .vimrc file, do not restore 'cpo'
 
 # ifdef FEAT_PROFILE
     int		sn_prof_on;	// TRUE when script is/was profiled
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 8975e1b..f79112e 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -4270,18 +4270,64 @@
   delete('Xclose')
   delete('Xdone')
 
-  writefile(['vim9script'], 'XanotherScript')
+  writefile(['vim9script', 'g:cpoval = &cpo'], 'XanotherScript')
   set cpo=aABceFsMny>
   edit XanotherScript
   so %
   assert_equal('aABceFsMny>', &cpo)
+  assert_equal('aABceFs', g:cpoval)
   :1del
+  setline(1, 'let g:cpoval = &cpo')
   w
   so %
   assert_equal('aABceFsMny>', &cpo)
+  assert_equal('aABceFsMny>', g:cpoval)
 
   delete('XanotherScript')
   set cpo&vim
+  unlet g:cpoval
+
+  if has('unix')
+    # 'cpo' is not restored in main vimrc
+    var save_HOME = $HOME
+    $HOME = getcwd() .. '/Xhome'
+    mkdir('Xhome')
+    var lines =<< trim END
+        vim9script
+        writefile(['before: ' .. &cpo], 'Xresult')
+        set cpo+=M
+        writefile(['after: ' .. &cpo], 'Xresult', 'a')
+    END
+    writefile(lines, 'Xhome/.vimrc')
+
+    lines =<< trim END
+        call writefile(['later: ' .. &cpo], 'Xresult', 'a')
+    END
+    writefile(lines, 'Xlegacy')
+
+    lines =<< trim END
+        vim9script
+        call writefile(['vim9: ' .. &cpo], 'Xresult', 'a')
+        qa
+    END
+    writefile(lines, 'Xvim9')
+
+    var cmd = GetVimCommand() .. " -S Xlegacy -S Xvim9"
+    cmd = substitute(cmd, '-u NONE', '', '')
+    exe "silent !" .. cmd
+
+    assert_equal([
+        'before: aABceFs',
+        'after: aABceFsM',
+        'later: aABceFsM',
+        'vim9: aABceFs'], readfile('Xresult'))
+
+    $HOME = save_HOME
+    delete('Xhome', 'rf')
+    delete('Xlegacy')
+    delete('Xvim9')
+    delete('Xresult')
+  endif
 enddef
 
 " Use :function so we can use Check commands
diff --git a/src/version.c b/src/version.c
index 1ada856..9a5ef2c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3901,
+/**/
     3900,
 /**/
     3899,