diff --git a/include/faabric/util/batch.h b/include/faabric/util/batch.h
index de8f906e2..56b8e964a 100644
--- a/include/faabric/util/batch.h
+++ b/include/faabric/util/batch.h
@@ -17,6 +17,9 @@ std::shared_ptr<faabric::BatchExecuteRequest> batchExecFactory(
 
 bool isBatchExecRequestValid(std::shared_ptr<faabric::BatchExecuteRequest> ber);
 
+void updateBatchExecAppId(std::shared_ptr<faabric::BatchExecuteRequest> ber,
+                          int newAppId);
+
 void updateBatchExecGroupId(std::shared_ptr<faabric::BatchExecuteRequest> ber,
                             int newGroupId);
 
diff --git a/src/util/batch.cpp b/src/util/batch.cpp
index 5262cbe0b..de5ad2d8b 100644
--- a/src/util/batch.cpp
+++ b/src/util/batch.cpp
@@ -61,12 +61,24 @@ bool isBatchExecRequestValid(std::shared_ptr<faabric::BatchExecuteRequest> ber)
     return true;
 }
 
+void updateBatchExecAppId(std::shared_ptr<faabric::BatchExecuteRequest> ber,
+                          int newAppId)
+{
+    ber->set_appid(newAppId);
+    for (int i = 0; i < ber->messages_size(); i++) {
+        ber->mutable_messages(i)->set_appid(newAppId);
+    }
+
+    // Sanity-check in debug mode
+    assert(isBatchExecRequestValid(ber));
+}
+
 void updateBatchExecGroupId(std::shared_ptr<faabric::BatchExecuteRequest> ber,
                             int newGroupId)
 {
     ber->set_groupid(newGroupId);
-    for (auto msg : *ber->mutable_messages()) {
-        msg.set_groupid(newGroupId);
+    for (int i = 0; i < ber->messages_size(); i++) {
+        ber->mutable_messages(i)->set_groupid(newGroupId);
     }
 
     // Sanity-check in debug mode
diff --git a/tests/test/util/test_batch.cpp b/tests/test/util/test_batch.cpp
index f664653b7..c4a7f8328 100644
--- a/tests/test/util/test_batch.cpp
+++ b/tests/test/util/test_batch.cpp
@@ -88,6 +88,21 @@ TEST_CASE("Test batch. exec request sanity checks")
     REQUIRE(isBerValid == isBatchExecRequestValid(ber));
 }
 
+TEST_CASE("Test updating the app ID of a BER")
+{
+    int nMessages = 4;
+    std::shared_ptr<faabric::BatchExecuteRequest> ber =
+      batchExecFactory("demo", "echo", nMessages);
+
+    // By default the BER is valid
+    REQUIRE(isBatchExecRequestValid(ber));
+
+    int newAppId = 1337;
+    updateBatchExecAppId(ber, newAppId);
+    REQUIRE(isBatchExecRequestValid(ber));
+    REQUIRE(ber->appid() == newAppId);
+}
+
 TEST_CASE("Test updating the group ID of a BER")
 {
     int nMessages = 4;