diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index a5ac678..012f134 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -375,7 +375,7 @@
             return null;
         }
         // vlan assignment is expensive but done only once
-        List<Ip4Prefix> configuredSubnets = deviceConfiguration.getSubnets(deviceId);
+        Set<Ip4Prefix> configuredSubnets = deviceConfiguration.getSubnets(deviceId);
         Set<Short> assignedVlans = new HashSet<>();
         Set<Ip4Prefix> unassignedSubnets = new HashSet<>();
         for (Ip4Prefix sub : configuredSubnets) {