diff --git a/hls4ml/model/flow/flow.py b/hls4ml/model/flow/flow.py
index 43415f5ac0..6a2185d721 100644
--- a/hls4ml/model/flow/flow.py
+++ b/hls4ml/model/flow/flow.py
@@ -62,10 +62,10 @@ def optimizers(self):
         return optimizers
 
     def _add_optimizer(self, opt_name):
-        self._added_optimizers.put(opt_name)
+        self._added_optimizers.add(opt_name)
 
     def _remove_optimizer(self, opt_name):
-        self._removed_optimizers.put(opt_name)
+        self._removed_optimizers.add(opt_name)
 
 
 flow_map = {}
diff --git a/test/pytest/test_flows.py b/test/pytest/test_flows.py
index e46dde70d6..297547e0e3 100644
--- a/test/pytest/test_flows.py
+++ b/test/pytest/test_flows.py
@@ -119,3 +119,9 @@ def test_flows(tester):
     expected = tester.expected_pass_order
     observed = tester.observed_pass_order
     assert success, f'Tester {i} fails: expected ({expected}), observed ({observed})'
+
+
+def test_update_dynamic_flow():
+    dynamic_flow = hls4ml.model.flow.register_flow('TestDynamicFlowUpdate', lambda: ['A', 'B'])
+    hls4ml.model.flow.update_flow(dynamic_flow, add_optimizers=['C'], remove_optimizers=['A'])
+    assert set(hls4ml.model.flow.get_flow(dynamic_flow).optimizers) == {'B', 'C'}