diff --git a/pacman/operations/router_algorithms/application_router.py b/pacman/operations/router_algorithms/application_router.py
index 5805bf240..bb2472a71 100644
--- a/pacman/operations/router_algorithms/application_router.py
+++ b/pacman/operations/router_algorithms/application_router.py
@@ -204,7 +204,8 @@ def route_application_graph() -> MulticastRoutingTableByPartition:
         # Get all source chips coordinates
         all_source_xys = {
             vertex_xy(m_vertex)
-            for m_vertex in source.machine_vertices}
+            for m_vertex in source.splitter.get_out_going_vertices(
+                partition.identifier)}
 
         # Keep track of the source edge chips
         source_edge_xys: Set[XY] = set()