diff --git a/rs/nns/governance/src/proposals/mod.rs b/rs/nns/governance/src/proposals/mod.rs
index e7f9046069b2..4b61fe08b09d 100644
--- a/rs/nns/governance/src/proposals/mod.rs
+++ b/rs/nns/governance/src/proposals/mod.rs
@@ -216,6 +216,12 @@ impl ValidProposalAction {
         env: Arc<dyn Environment>,
     ) -> Result<SelfDescribingProposalAction, GovernanceError> {
         match self {
+            // ExecuteNnsFunction is the only case where we need to call `canister_metadata` to get
+            // the candid file of an external canister, and hence it's the only one with `await`.
+            ValidProposalAction::ExecuteNnsFunction(execute_nns_function) => {
+                execute_nns_function.to_self_describing_action(env).await
+            }
+
             ValidProposalAction::Motion(motion) => Ok(motion.to_self_describing_action()),
             ValidProposalAction::ApproveGenesisKyc(approve_genesis_kyc) => {
                 Ok(approve_genesis_kyc.to_self_describing_action())
@@ -223,10 +229,6 @@ impl ValidProposalAction {
             ValidProposalAction::AddOrRemoveNodeProvider(add_or_remove_node_provider) => {
                 Ok(add_or_remove_node_provider.to_self_describing_action())
             }
-
-            ValidProposalAction::ExecuteNnsFunction(execute_nns_function) => {
-                execute_nns_function.to_self_describing_action(env).await
-            }
             ValidProposalAction::RegisterKnownNeuron(register_known_neuron) => {
                 Ok(register_known_neuron.to_self_describing_action())
             }
@@ -251,6 +253,9 @@ impl ValidProposalAction {
             ValidProposalAction::FulfillSubnetRentalRequest(fulfill_subnet_rental_request) => {
                 Ok(fulfill_subnet_rental_request.to_self_describing_action())
             }
+            ValidProposalAction::CreateServiceNervousSystem(create_service_nervous_system) => {
+                Ok(create_service_nervous_system.to_self_describing_action())
+            }
             _ => Err(GovernanceError::new_with_message(
                 ErrorType::InvalidProposal,
                 "Self describing proposal actions are not supported for this proposal action yet.",