diff --git a/grudge/trace_pair.py b/grudge/trace_pair.py
index d2f8aeb0..8f4583b1 100644
--- a/grudge/trace_pair.py
+++ b/grudge/trace_pair.py
@@ -319,14 +319,22 @@ def interior_trace_pair(dcoll: DiscretizationCollection, vec) -> TracePair:
     return local_interior_trace_pair(dcoll, vec)
 
 
-@dataclass(frozen=True)  # for KeyBuilder support
 class CommTag:
     """A communication tag with a hash value that is stable across
     runs, even without setting ``PYTHONHASHSEED``."""
+
     @memoize_method
-    def __hash__(self):
+    def __hash__(self) -> int:
         return hash(tuple(str(type(self)).encode("ascii")))
 
+    def __eq__(self, other: object) -> bool:
+        return type(self) is type(other)
+
+    def update_persistent_hash(self, key_hash, key_builder):
+        key_builder.rec(key_hash, (self.__class__.__module__,
+                                   self.__class__.__qualname__))
+
+
 
 def interior_trace_pairs(dcoll: DiscretizationCollection, vec, *,
         comm_tag: Optional[Hashable] = None, tag: Hashable = None,
diff --git a/test/test_trace_pair.py b/test/test_trace_pair.py
index 9e26032c..2d2bd782 100644
--- a/test/test_trace_pair.py
+++ b/test/test_trace_pair.py
@@ -22,7 +22,7 @@
 
 
 import numpy as np
-from grudge.trace_pair import TracePair, CommTag
+from grudge.trace_pair import TracePair
 import meshmode.mesh.generation as mgen
 from meshmode.dof_array import DOFArray
 from dataclasses import dataclass
@@ -72,6 +72,8 @@ def rand():
 
 def test_commtag(actx_factory):
 
+    from grudge.trace_pair import CommTag, _sym_tag_to_num_tag
+
     class DerivedCommTag(CommTag):
         pass
 
@@ -86,6 +88,8 @@ class DerivedDerivedCommTag(DerivedCommTag):
     dct2 = DerivedCommTag()
     ddct = DerivedDerivedCommTag()
 
+    assert _sym_tag_to_num_tag(ct) == 441551355
+
     assert ct == ct2
     assert ct != dct
     assert dct == dct2
@@ -110,27 +114,3 @@ class DerivedDerivedCommTag(DerivedCommTag):
     assert hash((dct, ct)) == 6599529611285265043
 
     # }}}
-
-    # {{{ test using derived dataclasses
-
-    @dataclass(frozen=True)
-    class DataCommTag(CommTag):
-        data: int
-
-    @dataclass(frozen=True)
-    class DataCommTag2(CommTag):
-        data: int
-
-    d1 = DataCommTag(1)
-    d2 = DataCommTag(2)
-    d3 = DataCommTag(1)
-
-    assert d1 != d2
-    assert hash(d1) != hash(d2)
-    assert d1 == d3
-    assert hash(d1) == hash(d3)
-
-    d4 = DataCommTag2(1)
-    assert d1 != d4
-
-    # }}}