diff --git a/lib/ansible/vars/__init__.py b/lib/ansible/vars/__init__.py
index b50fb22712..6e918d70e2 100644
--- a/lib/ansible/vars/__init__.py
+++ b/lib/ansible/vars/__init__.py
@@ -459,6 +459,8 @@ class VariableManager:
 
             templar.set_available_variables(vars_copy)
             delegated_host_name = templar.template(task.delegate_to, fail_on_undefined=False)
+            if not delegated_host_name:
+                raise AnsibleError(message="Undefined delegate_to host for task:", obj=task._ds)
             if delegated_host_name in delegated_host_vars:
                 # no need to repeat ourselves, as the delegate_to value
                 # does not appear to be tied to the loop item variable