diff --git a/server/src/uds/core/services/generics/fixed/service.py b/server/src/uds/core/services/generics/fixed/service.py
index ca3b96986..d059edddc 100644
--- a/server/src/uds/core/services/generics/fixed/service.py
+++ b/server/src/uds/core/services/generics/fixed/service.py
@@ -151,9 +151,16 @@ def initialize(self, values: 'types.core.ValuesType') -> None:
             if not self.machines.value:
                 raise exceptions.ui.ValidationError(gettext('We need at least a machine'))
 
-            # Remove machines not in values from "assigned" set
+            # Do not allow removing machines that still have assigned user services.
+            # (their UserService rows would linger, counting against userservices_limit)
             with self._assigned_access() as assigned_vms:
-                assigned_vms &= set(self.machines.as_list())
+                removed_assigned = assigned_vms - set(self.machines.as_list())
+                if removed_assigned:
+                    raise exceptions.ui.ValidationError(
+                        gettext('Cannot remove machines with assigned services: {}').format(
+                            ', '.join(sorted(removed_assigned))
+                        )
+                    )
             self.token.value = self.token.value.strip()
 
     @contextlib.contextmanager