diff --git a/ops/model.py b/ops/model.py
index 6b665c96f..4798b2804 100644
--- a/ops/model.py
+++ b/ops/model.py
@@ -618,12 +618,7 @@ def open_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
                 or ``port`` is not provided when ``protocol`` is 'tcp' or
                 'udp'.
         """
-        normalised_protocol : str = protocol.lower()
-        if normalised_protocol == 'icmp' and port is not None:
-            raise ModelError("icmp cannot have a port number specified")
-        elif normalised_protocol in ('tcp', 'udp') and port is None:
-            raise ModelError(f"{normalised_protocol} must have a port number specified")
-        self._backend.open_port(normalised_protocol, port)
+        self._backend.open_port(protocol.lower(), port)
 
     def close_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
                    port: Optional[int] = None) -> None:
@@ -651,12 +646,7 @@ def close_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
                 or ``port`` is not provided when ``protocol`` is 'tcp' or
                 'udp'.
         """
-        normalised_protocol : str = protocol.lower()
-        if normalised_protocol == 'icmp' and port is not None:
-            raise ModelError("icmp cannot have a port number specified")
-        elif normalised_protocol in ('tcp', 'udp') and port is None:
-            raise ModelError(f"{normalised_protocol} must have a port number specified")
-        self._backend.close_port(normalised_protocol, port)
+        self._backend.close_port(protocol.lower(), port)
 
     def opened_ports(self) -> Set['Port']:
         """Return a list of opened ports for this unit."""
diff --git a/test/test_model.py b/test/test_model.py
index e8157c623..fb3236560 100755
--- a/test/test_model.py
+++ b/test/test_model.py
@@ -3337,11 +3337,6 @@ def test_open_port_error(self):
             ['open-port', '8080/ftp'],
         ])
 
-        with self.assertRaises(ops.ModelError) as cm:
-            self.unit.open_port('icmp', 8000)
-        with self.assertRaises(ops.ModelError) as cm:
-            self.unit.open_port('udp')
-
     def test_close_port(self):
         fake_script(self, 'close-port', 'exit 0')
 
@@ -3366,11 +3361,6 @@ def test_close_port_error(self):
             ['close-port', '8080/ftp'],
         ])
 
-        with self.assertRaises(ops.ModelError) as cm:
-            self.unit.close_port('icmp', 8000)
-        with self.assertRaises(ops.ModelError) as cm:
-            self.unit.close_port('udp')
-
     def test_opened_ports(self):
         fake_script(self, 'opened-ports', """echo 8080/tcp; echo icmp""")