diff --git a/carnot/carnot_vote_aggregation.py b/carnot/carnot_vote_aggregation.py
index 1cddacd..1d1c503 100644
--- a/carnot/carnot_vote_aggregation.py
+++ b/carnot/carnot_vote_aggregation.py
@@ -272,28 +272,32 @@ class Carnot2(Carnot):
 
         return concatenated_qc
 
-    # Similarly aggregated qcs are concatenated after timeout t2:
-    def concatenate_aggregate_qcs(qc_set: Set[AggregateQc]) -> AggregateQc:
-        # Initialize the attributes for the concatenated AggregateQc
+    # Similarly aggregated qcs are concatenated after timeout t2.
+    from typing import Set, List, Optional, Union
+
+    # Define your types here (Id, View, StandardQc, AggregateQc, etc.)
+
+    def concatenate_aggregate_qcs(qc_set: Set[Union[StandardQc, AggregateQc]]) -> AggregateQc:
+        if qc_set is None:
+            return None
+
         concatenated_qcs = []
         concatenated_view = None
         concatenated_sender_ids = set()
         highest_standard_qc = None
 
-        # Iterate through the input set of AggregateQc objects
         for qc in qc_set:
-            concatenated_qcs.extend(qc.qcs)
-            concatenated_sender_ids.update(qc.sender_ids)
+            if isinstance(qc, AggregateQc):
+                concatenated_qcs.extend(qc.qcs)
+                concatenated_sender_ids.update(qc.sender_ids)
 
-            # Choose the view value from the first AggregateQc in the set
-            if concatenated_view is None:
-                concatenated_view = qc.view
+                if concatenated_view is None:
+                    concatenated_view = qc.view
 
-            # Find the highest StandardQc among the AggregateQc.high_qc.view fields
-            if highest_standard_qc is None or qc.high_qc.view > highest_standard_qc.view:
-                highest_standard_qc = qc.high_qc
+                if highest_standard_qc is None or (isinstance(qc.highest_qc, StandardQc) and
+                                                   qc.highest_qc.view > highest_standard_qc.view):
+                    highest_standard_qc = qc.highest_qc
 
-        # Create the concatenated AggregateQc object
         concatenated_aggregate_qc = AggregateQc(
             qcs=concatenated_qcs,
             highest_qc=highest_standard_qc,
@@ -369,3 +373,5 @@ class Carnot2(Carnot):
             sender=self.id
         )
         return Send(payload=timeout_msg, to=self.overlay.my_committee())
+
+
diff --git a/carnot/my_carnot.py b/carnot/my_carnot.py
index ee72ddd..cfd9907 100644
--- a/carnot/my_carnot.py
+++ b/carnot/my_carnot.py
@@ -74,10 +74,11 @@ class StandardQc:
 
 @dataclass
 class AggregateQc:
+    sender_ids: Set[Id]
     qcs: List[View]
     highest_qc: StandardQc
     view: View
-    sender_ids: Set[Id]
+
 
     def view(self) -> View:
         return self.view
@@ -86,6 +87,9 @@ class AggregateQc:
         assert self.highest_qc.get_view == max(self.qcs)
         return self.highest_qc
 
+    def __hash__(self):
+        # Define a hash function based on the attributes that need to be considered for hashing
+        return hash((frozenset(self.sender_ids), tuple(self.qcs), self.highest_qc, self.view))
 
 Qc: TypeAlias = StandardQc | AggregateQc
 
diff --git a/carnot/test_carnot_vote_aggregation.py b/carnot/test_carnot_vote_aggregation.py
index 22ad062..0cc2693 100644
--- a/carnot/test_carnot_vote_aggregation.py
+++ b/carnot/test_carnot_vote_aggregation.py
@@ -1,7 +1,7 @@
 import unittest
 
 import carnot
-from carnot import merging_committees
+from carnot.carnot_vote_aggregation import  AggregateQc
 from carnot.merging_committees import merge_committees
 import itertools
 import unittest
@@ -49,5 +49,49 @@ class TestConcatenateStandardQcs(unittest.TestCase):
         self.assertEqual(concatenated_qc, expected_qc)
 
 
+class TestConcatenateAggregateQcs(unittest.TestCase):
+
+    def test_concatenate_aggregate_qcs_single_qc(self):
+        # Test concatenating a single AggregateQc
+        qc1 = AggregateQc(
+            sender_ids={1, 2, 3},
+            qcs=[1, 2, 3],
+            highest_qc=3,
+            view=1
+        )
+        aggregate_qcs = {qc1}
+        concatenated_qc = carnot.carnot_vote_aggregation.Carnot2.concatenate_aggregate_qcs(aggregate_qcs)
+        self.assertEqual(concatenated_qc, qc1)
+
+    def test_concatenate_aggregate_qcs_multiple_qcs(self):
+        # Test concatenating multiple AggregateQcs
+        qc1 = AggregateQc(
+            sender_ids={1, 2, 3},
+            qcs=[1, 2, 3],
+            highest_qc=3,
+            view=1
+        )
+        qc2 = AggregateQc(
+            sender_ids={4, 5, 6},
+            qcs=[4, 5, 6],
+            highest_qc=6,
+            view=2
+        )
+        qc3 = AggregateQc(
+            sender_ids={7, 8, 9},
+            qcs=[7, 8, 9],
+            highest_qc=9,
+            view=3
+        )
+        aggregate_qcs = {qc1, qc2, qc3}
+        concatenated_qc = carnot.carnot_vote_aggregation.Carnot2.concatenate_aggregate_qcs(aggregate_qcs)
+
+        # Assert that the concatenated AggregateQc has the correct attributes
+        self.assertEqual(concatenated_qc.sender_ids, {1, 2, 3, 4, 5, 6, 7, 8, 9})
+        self.assertEqual(concatenated_qc.qcs, [1, 2, 3, 4, 5, 6, 7, 8, 9])
+        self.assertEqual(concatenated_qc.highest_qc, 9)
+        self.assertEqual(concatenated_qc.view, 1)  # View should be from the first QC
+
+
 if __name__ == '__main__':
     unittest.main()