diff --git a/vnet_manager/config/validate.py b/vnet_manager/config/validate.py
index 056b26e..9258e8b 100644
--- a/vnet_manager/config/validate.py
+++ b/vnet_manager/config/validate.py
@@ -244,6 +244,12 @@ def validate_interface_config(self, machine: str):
             if "mac" not in int_vals:
                 logger.debug(f"MAC not found for interface {int_name} on machine {machine}, generating a random one")
                 self._new_config["machines"][machine]["interfaces"][int_name]["mac"] = random_mac_generator()
+            elif isinstance(int_vals["mac"], int):
+                logger.error(
+                    f"MAC {int_vals['mac']} for interface {int_name} on machine {machine} was parsed as a sexagesimal integer. "
+                    "Please wrap the MAC address in 'quotes'"
+                )
+                self._all_ok = False
             # From: https://stackoverflow.com/a/7629690/8632038
             elif not fullmatch(r"^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$", int_vals["mac"]):
                 logger.error(
diff --git a/vnet_manager/tests/config/test_validate.py b/vnet_manager/tests/config/test_validate.py
index 8470473..161163a 100644
--- a/vnet_manager/tests/config/test_validate.py
+++ b/vnet_manager/tests/config/test_validate.py
@@ -197,6 +197,24 @@ def test_validate_machine_config_fails_if_bridge_config_is_not_a_dict(self):
         self.assertFalse(self.validator.config_validation_successful)
         self.logger.error.assert_called_once()
 
+    def test_validate_interface_config_sexagesimal_mac_address(self):
+        # 0d33212743741 is the sexagesimal representation of 42:42:42:42:09:01
+        # cf. https://github.com/Erik-Lamers1/vnet-manager/issues/62
+        self.validator.config["machines"]["router100"]["interfaces"]["eth12"]["mac"] = 33212743741
+        self.validator.validate_interface_config("router100")
+        self.assertFalse(self.validator.config_validation_successful)
+        self.logger.error.assert_called_once_with(
+            f"MAC 33212743741 for interface eth12 on machine router100 was parsed as a sexagesimal integer. Please wrap the MAC address in 'quotes'"
+        )
+
+    def test_validate_interface_config_invalid_mac_address(self):
+        self.validator.config["machines"]["router100"]["interfaces"]["eth12"]["mac"] = "gg:hh:ii:jj:kk:ll"
+        self.validator.validate_interface_config("router100")
+        self.assertFalse(self.validator.config_validation_successful)
+        self.logger.error.assert_called_once_with(
+            f"MAC gg:hh:ii:jj:kk:ll for interface eth12 on machine router100, does not seem to be valid. Please check your settings"
+        )
+
 
 class TestValidateConfigValidateMachineFilesParameters(VNetTestCase):
     def setUp(self) -> None: