diff --git a/server/src/main/java/com/mirth/connect/server/userutil/DestinationSet.java b/server/src/main/java/com/mirth/connect/server/userutil/DestinationSet.java
index 76e1ff6e0..39abb862a 100644
--- a/server/src/main/java/com/mirth/connect/server/userutil/DestinationSet.java
+++ b/server/src/main/java/com/mirth/connect/server/userutil/DestinationSet.java
@@ -44,7 +44,9 @@ public DestinationSet(ImmutableConnectorMessage connectorMessage) {
         Set<Integer> metaDataIds = null;
 
         try {
-            if (connectorMessage.getSourceMap().get(Constants.DESTINATION_SET_KEY) instanceof Set<?> set) {
+            // No pattern matching here: the client's reference parser only understands Java 5 syntax
+            Object set = connectorMessage.getSourceMap().get(Constants.DESTINATION_SET_KEY);
+            if (set instanceof Set) {
                 destinationIdMap = connectorMessage.getDestinationIdMap();
                 metaDataIds = (Set<Integer>) set;
             }