diff --git a/pySim-shell.py b/pySim-shell.py
index 7aaa2343..c2bb15c2 100755
--- a/pySim-shell.py
+++ b/pySim-shell.py
@@ -53,6 +53,7 @@ from pySim.transport import init_reader, ApduTracer, argparse_add_reader_args, P
 from pySim.cards import card_detect, SimCardBase, UiccCardBase
 from pySim.utils import h2b, b2h, i2h, swap_nibbles, rpad, JsonEncoder, bertlv_parse_one, sw_match
 from pySim.utils import sanitize_pin_adm, tabulate_str_list, boxed_heading_str, Hexstr, dec_iccid
+from pySim.utils import is_hexstr_or_decimal
 from pySim.card_handler import CardHandler, CardHandlerAuto
 
 from pySim.filesystem import CardDF, CardADF, CardModel, CardApplication
@@ -777,7 +778,7 @@ class PySimCommands(CommandSet):
             self._cmd.poutput("no description available")
 
     verify_adm_parser = argparse.ArgumentParser()
-    verify_adm_parser.add_argument('ADM1', nargs='?', type=str,
+    verify_adm_parser.add_argument('ADM1', nargs='?', type=is_hexstr_or_decimal,
                                    help='ADM1 pin value. If none given, CSV file will be queried')
 
     @cmd2.with_argparser(verify_adm_parser)
diff --git a/pySim/utils.py b/pySim/utils.py
index 7459a3f4..92bf70ff 100644
--- a/pySim/utils.py
+++ b/pySim/utils.py
@@ -1467,3 +1467,14 @@ class CardCommandSet:
 def all_subclasses(cls) -> set:
     """Recursively get all subclasses of a specified class"""
     return set(cls.__subclasses__()).union([s for c in cls.__subclasses__() for s in all_subclasses(c)])
+
+def is_hexstr_or_decimal(instr: str) -> str:
+    """Method that can be used as 'type' in argparse.add_argument() to validate the value consists of
+    [hexa]decimal digits only."""
+    if instr.isdecimal():
+        return instr
+    if not all(c in string.hexdigits for c in instr):
+        raise ValueError('Input must be [hexa]decimal')
+    if len(instr) & 1:
+        raise ValueError('Input has un-even number of hex digits')
+    return instr