diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index fa7febc..8eb60be 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1,4 +1,4 @@
-*vim9.txt*	For Vim version 8.2.  Last change: 2020 Aug 15
+*vim9.txt*	For Vim version 8.2.  Last change: 2020 Aug 27
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -49,6 +49,7 @@
 The Vim9 script syntax and semantics are used in:
 - a function defined with the `:def` command
 - a script file where the first command is `vim9script`
+- an autocommand defined in the context of these
 
 When using `:function` in a Vim9 script file the legacy syntax is used.
 However, this can be confusing and is therefore discouraged.
@@ -92,9 +93,13 @@
 Many errors are already found when compiling, before the function is executed.
 The syntax is strict, to enforce code that is easy to read and understand.
 
-Compilation is done when the function is first called, or when the
-`:defcompile` command is encountered in the script where the function was
-defined. `:disassemble` also compiles the function.
+Compilation is done when:
+- the function is first called
+- when the `:defcompile` command is encountered in the script where the
+  function was defined
+- `:disassemble` is used for the function.
+- a function that is compiled calls the function or uses it as a function
+  reference
 
 `:def` has no options like `:function` does: "range", "abort", "dict" or
 "closure".  A `:def` function always aborts on an error, does not get a range
@@ -492,6 +497,18 @@
 	    use-feature
 	  enddef
 	endif
+Of put the unsupported code inside an `if` with a constant expression that
+evaluates to false: >
+	def Maybe()
+	  if has('feature')
+	    use-feature
+	  endif
+	enddef
+Note that for unrecognized commands there is no check for "|" and a following
+command.  This will give an error for missing `endif`: >
+	def Maybe()
+	  if has('feature') | use-feature | endif
+	enddef
 
 ==============================================================================
 
@@ -539,7 +556,7 @@
 variables can be accessed without the "s:" prefix.  They must be defined
 before the function is compiled.  If the script the function is defined in is
 legacy script, then script-local variables must be accessed with the "s:"
-prefix.
+prefix and they do not need to exist (they can be deleted any time).
 
 						*:defc* *:defcompile*
 :defc[ompile]		Compile functions defined in the current script that
@@ -692,6 +709,22 @@
 	['a', 'b', 'c']	list<string>
 	[1, 'x', 3]	list<any>
 
+
+Stricter type checking					*type-checking*
+
+In legacy Vim script, where a number was expected, a string would be
+automatically converted to a number.  This was convenient for an actual number
+such as "123", but leads to unexpected problems (but no error message) if the
+string doesn't start with a number.  Quite often this leads to hard-to-find
+bugs.
+
+In Vim9 script this has been made stricter.  In most places it works just as
+before, if the expected type was already.  There will sometimes be an error,
+thus breaking backwards compatibility.  For example:
+- Using a number other than 0 or 1 where a boolean is expected.  *E1023*
+- Using a string value when setting a number options.
+- Using a number where a string is expected.   *E1024*
+
 ==============================================================================
 
 5.  Namespace, Import and Export
@@ -703,6 +736,9 @@
 the script is local, unless exported.  Those exported items, and only those
 items, can then be imported in another script.
 
+You can cheat by using the global namespace explicitly.  We will assume here
+that you don't do that.
+
 
 Namespace ~
 							*:vim9script* *:vim9*