diff --git a/x-pack/legacy/plugins/apm/public/components/app/ServiceMap/get_cytoscape_elements.test.ts b/x-pack/legacy/plugins/apm/public/components/app/ServiceMap/get_cytoscape_elements.test.ts
new file mode 100644
index 0000000000000..594b00c568f24
--- /dev/null
+++ b/x-pack/legacy/plugins/apm/public/components/app/ServiceMap/get_cytoscape_elements.test.ts
@@ -0,0 +1,121 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { getCytoscapeElements } from './get_cytoscape_elements';
+
+describe('getCytoscapeElements', () => {
+  describe('with an empty list', () => {
+    it('returns an empty list', () => {
+      expect(getCytoscapeElements([], '')).toEqual([]);
+    });
+  });
+
+  describe('with an external and a service with the same destination.address', () => {
+    it('only returns the service', () => {
+      const responses = [
+        {
+          after: undefined,
+          connections: [
+            {
+              source: {
+                'service.environment': null,
+                'service.name': 'client',
+                'service.framework.name': null,
+                'agent.name': 'js-base'
+              },
+              destination: {
+                'destination.address': 'opbeans-node',
+                'span.subtype': null,
+                'span.type': 'resource'
+              }
+            },
+            {
+              source: {
+                'service.environment': null,
+                'service.name': 'client',
+                'service.framework.name': null,
+                'agent.name': 'js-base'
+              },
+              destination: {
+                'service.environment': 'production',
+                'service.name': 'opbeans-node',
+                'service.framework.name': null,
+                'agent.name': 'nodejs'
+              }
+            }
+          ],
+          discoveredServices: [],
+          services: [
+            {
+              'service.name': 'client',
+              'agent.name': 'js-base',
+              'service.environment': null,
+              'service.framework.name': null
+            }
+          ]
+        }
+      ];
+
+      const returnValue = [
+        {
+          group: 'nodes',
+          data: {
+            id: 'client',
+            label: 'client',
+            href:
+              '#/services/client/service-map?rangeFrom=now-24h&rangeTo=now&refreshPaused=true&refreshInterval=0',
+            agentName: 'js-base',
+            frameworkName: null,
+            type: 'service'
+          }
+        },
+        {
+          group: 'nodes',
+          data: {
+            id: '>opbeans-node',
+            label: 'opbeans-node',
+            type: 'resource',
+            subtype: null
+          }
+        },
+        {
+          group: 'nodes',
+          data: {
+            id: 'opbeans-node',
+            label: 'opbeans-node',
+            href:
+              '#/services/opbeans-node/service-map?rangeFrom=now-24h&rangeTo=now&refreshPaused=true&refreshInterval=0',
+            agentName: 'nodejs',
+            frameworkName: null,
+            type: 'service'
+          }
+        },
+        {
+          group: 'edges',
+          classes: undefined,
+          data: {
+            id: 'client~>opbeans-node',
+            source: 'client',
+            target: '>opbeans-node',
+            bidirectional: undefined
+          }
+        },
+        {
+          group: 'edges',
+          classes: undefined,
+          data: {
+            id: 'client~opbeans-node',
+            source: 'client',
+            target: 'opbeans-node',
+            bidirectional: undefined
+          }
+        }
+      ];
+
+      expect(getCytoscapeElements(responses, '')).toEqual(returnValue);
+    });
+  });
+});
diff --git a/x-pack/plugins/apm/common/service_map.ts b/x-pack/plugins/apm/common/service_map.ts
index f4354baa97655..b79f7e8d505db 100644
--- a/x-pack/plugins/apm/common/service_map.ts
+++ b/x-pack/plugins/apm/common/service_map.ts
@@ -16,7 +16,7 @@ export interface ServiceConnectionNode {
 export interface ExternalConnectionNode {
   'destination.address': string;
   'span.type': string;
-  'span.subtype': string;
+  'span.subtype': string | null;
 }
 
 export type ConnectionNode = ServiceConnectionNode | ExternalConnectionNode;