diff --git a/substra/sdk/backends/local/dal.py b/substra/sdk/backends/local/dal.py
index a3e1333d..f804a3c4 100644
--- a/substra/sdk/backends/local/dal.py
+++ b/substra/sdk/backends/local/dal.py
@@ -142,7 +142,11 @@ def get_performances(self, key: str) -> models.Performances:
                     performances.worker.append(task.worker)
                     performances.task_key.append(task.key)
                     performances.task_rank.append(task.rank)
-                    performances.round_idx.append(int(task.metadata.get("round_idx")))
+                    try:
+                        round_idx = int(task.metadata.get("round_idx"))
+                    except TypeError:
+                        round_idx = None
+                    performances.round_idx.append(round_idx)
                     performances.identifier.append(output.identifier)
                     performances.performance.append(output.asset)
 
diff --git a/substra/sdk/backends/remote/backend.py b/substra/sdk/backends/remote/backend.py
index c5976360..2d115985 100644
--- a/substra/sdk/backends/remote/backend.py
+++ b/substra/sdk/backends/remote/backend.py
@@ -97,7 +97,11 @@ def get_performances(self, key: str) -> models.Performances:
             performances.worker.append(test_task["compute_task"]["worker"])
             performances.task_key.append(test_task["compute_task"]["key"])
             performances.task_rank.append(test_task["compute_task"]["rank"])
-            performances.round_idx.append(int(test_task["compute_task"]["round_idx"]))
+            try:
+                round_idx = int(test_task["compute_task"]["round_idx"])
+            except TypeError:
+                round_idx = None
+            performances.round_idx.append(round_idx)
             performances.identifier.append(test_task["identifier"])
             performances.performance.append(test_task["perf"])