diff --git a/docs/shell.rst b/docs/shell.rst
index 4742b8e1..7022b5a2 100644
--- a/docs/shell.rst
+++ b/docs/shell.rst
@@ -400,7 +400,19 @@ verify_chv
 
 deactivate_file
 ~~~~~~~~~~~~~~~
-Deactivate the currently selected file.  This used to be called INVALIDATE in TS 11.11.
+Deactivate the currently selected file.  A deactivated file can no longer be accessed
+for any further operation (such as selecting and subsequently reading or writing).
+
+Any access to a file that is deactivated will trigger the error
+*SW 6283 'Selected file invalidated/disabled'*
+
+In order to re-access a deactivated file, you need to activate it again, see the
+`activate_file` command below.  Note that for *deactivation* the to-be-deactivated
+EF must be selected, but for *activation*, the DF above the to-be-activated
+EF must be selected!
+
+This command sends a DEACTIVATE FILE APDU to
+the card (used to be called INVALIDATE in TS 11.11 for classic SIM).
 
 
 activate_file
diff --git a/pySim-shell.py b/pySim-shell.py
index 6ff484b6..c6454038 100755
--- a/pySim-shell.py
+++ b/pySim-shell.py
@@ -882,8 +882,15 @@ class Iso7816Commands(CommandSet):
     activate_file_parser.add_argument('NAME', type=str, help='File name or FID of file to activate')
     @cmd2.with_argparser(activate_file_parser)
     def do_activate_file(self, opts):
-        """Activate the specified EF. This used to be called REHABILITATE in TS 11.11 for classic
-        SIM.  You need to specify the name or FID of the file to activate."""
+        """Activate the specified EF by sending an ACTIVATE FILE apdu command (used to be called REHABILITATE
+in TS 11.11 for classic SIM).
+
+This command is used to (re-)activate a file that is currently in deactivated (sometimes also called
+"invalidated") state.  You need to call this from the DF above the to-be-activated EF and specify the name or
+FID of the file to activate.
+
+Note that for *deactivation* the to-be-deactivated EF must be selected, but for *activation*, the DF
+above the to-be-activated EF must be selected!"""
         (data, sw) = self._cmd.lchan.activate_file(opts.NAME)
 
     def complete_activate_file(self, text, line, begidx, endidx) -> List[str]:
diff --git a/pySim/ts_102_221.py b/pySim/ts_102_221.py
index 308fc4a3..65dd87d9 100644
--- a/pySim/ts_102_221.py
+++ b/pySim/ts_102_221.py
@@ -808,7 +808,7 @@ class CardProfileUICC(CardProfile):
                 '6200': 'No information given, state of non-volatile memory unchanged',
                 '6281': 'Part of returned data may be corrupted',
                 '6282': 'End of file/record reached before reading Le bytes or unsuccessful search',
-                '6283': 'Selected file invalidated',
+                '6283': 'Selected file invalidated/disabled; needs to be activated before use',
                 '6284': 'Selected file in termination state',
                 '62f1': 'More data available',
                 '62f2': 'More data available and proactive command pending',