diff --git a/pytools/tag.py b/pytools/tag.py
index cc6922ccead2ed61a1e81633ea4fadc0c713bda1..0eff8f4fe56e04c8ceb0f8887406ecc9c6c43497 100644
--- a/pytools/tag.py
+++ b/pytools/tag.py
@@ -28,6 +28,20 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
 
+from pytools import memoize
+
+
+@memoize
+def _immediate_unique_tag_descendants(cls):
+    if UniqueTag in cls.__bases__:
+        return frozenset([cls])
+    else:
+        result = frozenset()
+        for base in cls.__bases__:
+            result = result | _immediate_unique_tag_descendants(base)
+        return result
+
+
 # {{{ docs
 
 __doc__ = """
@@ -90,6 +104,7 @@ class DottedName:
 
 # }}}
 
+
 # {{{ tag
 
 tag_dataclass = dataclass(init=True, eq=True, frozen=True, repr=True)
@@ -118,6 +133,10 @@ class Tag:
     def tag_name(self) -> DottedName:
         return DottedName.from_class(type(self))
 
+# }}}
+
+
+# {{{ unique tag
 
 class UniqueTag(Tag):
     """
@@ -126,12 +145,16 @@ class UniqueTag(Tag):
     """
     pass
 
+# }}}
+
 
 TagsType = FrozenSet[Tag]
 TagOrIterableType = Union[Iterable[Tag], Tag, None]
 T_co = TypeVar("T_co", bound="Taggable")
 
 
+# {{{ taggable
+
 class Taggable:
     """
     Parent class for objects with a `tags` attribute.
@@ -184,8 +207,15 @@ class Taggable:
                 for c in in_class.__bases__:
                     _check_recursively(c, class_set)
 
+        unique_tag_descendants = set()
         for tag in self.tags:
-            _check_recursively(type(tag), class_set)
+            tag_unique_tag_descendants = _immediate_unique_tag_descendants(
+                    type(tag))
+            intersection = unique_tag_descendants & tag_unique_tag_descendants
+            if intersection:
+                raise ValueError("Multiple tags are direct subclasses of "
+                        "the following UniqueTag(s): "
+                        f"{', '.join(d.__name__ for d in intersection)}")
 
     def copy(self: T_co, **kwargs: Any) -> T_co:
         """