diff --git a/tensorboard/dataclass_compat.py b/tensorboard/dataclass_compat.py
index a9b001a381..e0592854d6 100644
--- a/tensorboard/dataclass_compat.py
+++ b/tensorboard/dataclass_compat.py
@@ -78,7 +78,11 @@ def _migrate_graph_event(old_event, experimental_filter_graph=False):
     if experimental_filter_graph:
         try:
             graph_def = graph_pb2.GraphDef().FromString(graph_bytes)
-        except message.DecodeError:
+        # The reason for the RuntimeWarning catch here is b/27494216, whereby
+        # some proto parsers incorrectly raise that instead of DecodeError
+        # on certain kinds of malformed input.  Triggering this seems to require
+        # a combination of mysterious circumstances.
+        except (message.DecodeError, RuntimeWarning):
             logger.warning(
                 "Could not parse GraphDef of size %d. Skipping.",
                 len(graph_bytes),
diff --git a/tensorboard/dataclass_compat_test.py b/tensorboard/dataclass_compat_test.py
index 5985287826..4105b92338 100644
--- a/tensorboard/dataclass_compat_test.py
+++ b/tensorboard/dataclass_compat_test.py
@@ -23,6 +23,8 @@
 import numpy as np
 import tensorflow as tf
 
+from google.protobuf import message
+
 from tensorboard import dataclass_compat
 from tensorboard.backend.event_processing import event_file_loader
 from tensorboard.compat.proto import event_pb2
@@ -39,6 +41,12 @@
 from tensorboard.util import tensor_util
 from tensorboard.util import test_util
 
+try:
+    # python version >= 3.3
+    from unittest import mock
+except ImportError:
+    import mock  # pylint: disable=unused-import
+
 
 class MigrateEventTest(tf.test.TestCase):
     """Tests for `migrate_event`."""
@@ -254,14 +262,16 @@ def test_graph_def_experimental_filter_graph(self):
         self.assertProtoEquals(expected_graph_def, new_graph_def)
 
     def test_graph_def_experimental_filter_graph_corrupt(self):
-        # Simulate legacy graph event with an unparseable graph
+        # Simulate legacy graph event with an unparseable graph.
+        # We can't be sure whether this will produce `DecodeError` or
+        # `RuntimeWarning`, so we also check both cases below.
         old_event = event_pb2.Event()
         old_event.step = 0
         old_event.wall_time = 456.75
         # Careful: some proto parsers choke on byte arrays filled with 0, but
         # others don't (silently producing an empty proto, I guess).
         # Thus `old_event.graph_def = bytes(1024)` is an unreliable example.
-        old_event.graph_def = b"bogus"
+        old_event.graph_def = b"<malformed>"
 
         new_events = self._migrate_event(
             old_event, experimental_filter_graph=True
@@ -271,6 +281,50 @@ def test_graph_def_experimental_filter_graph_corrupt(self):
         self.assertLen(new_events, 1)
         self.assertProtoEquals(new_events[0], old_event)
 
+    def test_graph_def_experimental_filter_graph_DecodeError(self):
+        # Simulate raising DecodeError when parsing a graph event
+        old_event = event_pb2.Event()
+        old_event.step = 0
+        old_event.wall_time = 456.75
+        old_event.graph_def = b"<malformed>"
+
+        with mock.patch(
+            "tensorboard.compat.proto.graph_pb2.GraphDef"
+        ) as mockGraphDef:
+            instance = mockGraphDef.return_value
+            instance.FromString.side_effect = message.DecodeError
+
+            new_events = self._migrate_event(
+                old_event, experimental_filter_graph=True
+            )
+
+        # _migrate_event emits both the original event and the migrated event,
+        # but here there is no migrated event becasue the graph was unparseable.
+        self.assertLen(new_events, 1)
+        self.assertProtoEquals(new_events[0], old_event)
+
+    def test_graph_def_experimental_filter_graph_RuntimeWarning(self):
+        # Simulate raising RuntimeWarning when parsing a graph event
+        old_event = event_pb2.Event()
+        old_event.step = 0
+        old_event.wall_time = 456.75
+        old_event.graph_def = b"<malformed>"
+
+        with mock.patch(
+            "tensorboard.compat.proto.graph_pb2.GraphDef"
+        ) as mockGraphDef:
+            instance = mockGraphDef.return_value
+            instance.FromString.side_effect = RuntimeWarning
+
+            new_events = self._migrate_event(
+                old_event, experimental_filter_graph=True
+            )
+
+        # _migrate_event emits both the original event and the migrated event,
+        # but here there is no migrated event becasue the graph was unparseable.
+        self.assertLen(new_events, 1)
+        self.assertProtoEquals(new_events[0], old_event)
+
 
 if __name__ == "__main__":
     tf.test.main()