diff --git a/test/support/agent-singleton-mock.js b/test/support/agent-singleton-mock.js
index 3a8f56b3..06d517cd 100644
--- a/test/support/agent-singleton-mock.js
+++ b/test/support/agent-singleton-mock.js
@@ -248,6 +248,10 @@ class MockAgent extends Agent {
 }
 
 function portProperties(conf) {
+    if (!conf) {
+        return conf
+    }
+
     if (typeof conf !== 'number') {
         if (conf.collector) {
             return conf