diff --git a/meta/io.murano/Classes/resources/ExistingNeutronNetwork.yaml b/meta/io.murano/Classes/resources/ExistingNeutronNetwork.yaml
index 8e969476b..b7c7e4d02 100644
--- a/meta/io.murano/Classes/resources/ExistingNeutronNetwork.yaml
+++ b/meta/io.murano/Classes/resources/ExistingNeutronNetwork.yaml
@@ -81,8 +81,7 @@ Workflow:
               $.device_id in $routerCandidates and $.network_id != $this._internalNetworkId).
               select($.network_id)
           - $externalNetwork: $._getNetworks().where(
-              $.get('router:external') = true and $.id in $networkCandidates).
-              firstOrDefault()
+              $.get('router:external') = true and $.id in $networkCandidates).first(null)
           - If: $externalNetwork != null
             Then:
               - $.externalNetworkName: $externalNetwork.name
@@ -91,7 +90,7 @@ Workflow:
       - If: $.externalNetworkName = null
         Then:
           $.externalNetworkName: $._getNetworks().where(
-            $.get('router:external') = true).select($.name).firstOrDefault()
+            $.get('router:external') = true).select($.name).first(null)
       - If: $._externalNetworkId = null and $.externalNetworkName != null
         Then:
           $._externalNetworkId: $._getNetworks().where(
diff --git a/meta/io.murano/Classes/resources/Instance.yaml b/meta/io.murano/Classes/resources/Instance.yaml
index 50e838acd..e53961092 100644
--- a/meta/io.murano/Classes/resources/Instance.yaml
+++ b/meta/io.murano/Classes/resources/Instance.yaml
@@ -202,7 +202,7 @@ Methods:
                 Else:
                   - If: $.networks.customNetworks!= null
                     Then:
-                      - $._primaryNetwork: $.networks.customNetworks.firstOrDefault()
+                      - $._primaryNetwork: $.networks.customNetworks.first(null)
 
   ensureNetworksDeployed:
     Body: