--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -335,6 +335,8 @@ BufDelete			Before deleting a buffer fro
 				NOTE: When this autocommand is executed, the
 				current buffer "%" may be different from the
 				buffer being deleted "<afile>" and "<abuf>".
+				Don't change to another buffer, it will cause
+				problems.
 							*BufEnter*
 BufEnter			After entering a buffer.  Useful for setting
 				options for a file type.  Also executed when
@@ -397,6 +399,8 @@ BufUnload			Before unloading a buffer.  
 				NOTE: When this autocommand is executed, the
 				current buffer "%" may be different from the
 				buffer being unloaded "<afile>".
+				Don't change to another buffer, it will cause
+				problems.
 							*BufWinEnter*
 BufWinEnter			After a buffer is displayed in a window.  This
 				can be when the buffer is loaded (after
@@ -428,6 +432,8 @@ BufWipeout			Before completely deleting 
 				NOTE: When this autocommand is executed, the
 				current buffer "%" may be different from the
 				buffer being deleted "<afile>".
+				Don't change to another buffer, it will cause
+				problems.
 						*BufWrite* *BufWritePre*
 BufWrite or BufWritePre		Before writing the whole buffer to a file.
 							*BufWriteCmd*
@@ -748,8 +754,10 @@ SwapExists			Detected an existing swap f
 					'a'	abort, like hitting CTRL-C
 				When set to an empty string the user will be
 				asked, as if there was no SwapExists autocmd.
-				Note: Do not try to change the buffer, the
-				results are unpredictable.
+							*E812*
+				It is not allowed to change to another buffer,
+				change a buffer name or change directory
+				here.
 							*Syntax*
 Syntax				When the 'syntax' option has been set.  The
 				pattern is matched against the syntax name.