diff --git a/callagent/tests/SIPCallAgentTest.st b/callagent/tests/SIPCallAgentTest.st
index ff62780..610a914 100644
--- a/callagent/tests/SIPCallAgentTest.st
+++ b/callagent/tests/SIPCallAgentTest.st
@@ -126,9 +126,11 @@ TestCase subclass: SIPCallAgentTest [
     ]
 
     setUp [
+        | localSent |
         sent := OrderedCollection new.
+        localSent := sent.
         transport := SIPTransportMock new
-                        onData: [:datagram | sent add: datagram];
+                        onData: [:datagram | localSent add: datagram];
                         yourself.
         agent := SIPUserAgent createOn: transport.
         agent
diff --git a/callagent/tests/SIPInviteTest.st b/callagent/tests/SIPInviteTest.st
index 18118af..b873f4e 100644
--- a/callagent/tests/SIPInviteTest.st
+++ b/callagent/tests/SIPInviteTest.st
@@ -70,9 +70,11 @@ TestCase subclass: SIPInviteTest [
     ]
 
     setUp [
+        | localSent |
         sent := OrderedCollection new.
+        localSent := sent.
         transport := SIPTransportMock new
-                        onData: [:datagram | sent add: datagram];
+                        onData: [:datagram | localSent add: datagram];
                         yourself.
         agent := SIPUserAgent createOn: transport.
         agent
diff --git a/callagent/tests/SIPRegisterTransactionTest.st b/callagent/tests/SIPRegisterTransactionTest.st
index 1a6cee9..96e7952 100644
--- a/callagent/tests/SIPRegisterTransactionTest.st
+++ b/callagent/tests/SIPRegisterTransactionTest.st
@@ -53,9 +53,11 @@ TestCase subclass: SIPRegisterTransactionTest [
     ]
 
     setUp [
+        | localSent |
         sent := OrderedCollection new.
+        localSent := sent.
         transport := SIPTransportMock new
-                        onData: [:datagram | sent add: datagram];
+                        onData: [:datagram | localSent add: datagram];
                         yourself.
         agent := SIPUserAgent createOn: transport.
         agent