diff --git a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/FakeHandler.java b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/FakeHandler.java
index 2124ce2dbc..19680dbc23 100644
--- a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/FakeHandler.java
+++ b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/FakeHandler.java
@@ -38,7 +38,7 @@
 import static uk.co.real_logic.artio.library.FixLibrary.NO_MESSAGE_REPLAY;
 
 public class FakeHandler
-    implements SessionHandler, SessionAcquireHandler, SessionExistsHandler
+    implements SessionHandler, SessionAcquireHandler, SessionExistsHandler, LibraryConnectHandler
 {
     public static final String SESSION_START_ERROR = "Unexpected Error";
 
@@ -61,6 +61,8 @@ public class FakeHandler
 
     private boolean throwInOnSessionStart = false;
     private boolean onSessionStartCalled = false;
+    private int onLibraryConnectCalled = 0;
+    private int onLibraryDisconnectCalled = 0;
 
     {
         heartbeatEncoder.testReqID("abc");
@@ -388,4 +390,26 @@ public boolean onSessionStartCalled()
     {
         return onSessionStartCalled;
     }
+
+    @Override
+    public void onConnect(final FixLibrary library)
+    {
+        onLibraryConnectCalled++;
+    }
+
+    @Override
+    public void onDisconnect(final FixLibrary library)
+    {
+        onLibraryDisconnectCalled++;
+    }
+
+    public int isOnLibraryDisconnectCalled()
+    {
+        return onLibraryDisconnectCalled;
+    }
+
+    public int isOnLibraryConnectCalled()
+    {
+        return onLibraryConnectCalled;
+    }
 }
diff --git a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/MessageBasedAcceptorSystemTest.java b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/MessageBasedAcceptorSystemTest.java
index a652417deb..ca54a011f6 100644
--- a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/MessageBasedAcceptorSystemTest.java
+++ b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/MessageBasedAcceptorSystemTest.java
@@ -19,6 +19,7 @@
 import org.hamcrest.Matchers;
 import org.junit.Test;
 import org.mockito.ArgumentMatchers;
+
 import uk.co.real_logic.artio.*;
 import uk.co.real_logic.artio.builder.*;
 import uk.co.real_logic.artio.decoder.*;
@@ -110,6 +111,102 @@ public void shouldNotNotifyLibraryOfSessionUntilLoggedOn() throws IOException
         }
     }
 
+    /**
+     * This test is to track <a href="https://github.com/real-logic/artio/issues/529">Issue 529</a>
+     */
+    @Test(timeout = TEST_TIMEOUT_IN_MS)
+    public void shouldNotReceiveDuplicateMsgsAfterRequestingSessionFromEngine() throws IOException
+    {
+        setup(true, true);
+
+        final FakeOtfAcceptor fakeOtfAcceptor = new FakeOtfAcceptor();
+        final FakeHandler fakeHandler = new FakeHandler(fakeOtfAcceptor);
+        try (FixLibrary library = newAcceptingLibrary(fakeHandler, nanoClock))
+        {
+            final TestSystem ts = new TestSystem(library);
+            try (FixConnection connection = FixConnection.initiate(port))
+            {
+                library.poll(10);
+                assertFalse(fakeHandler.hasSeenSession());
+
+
+                //////////// GIVEN
+                // the client connects,
+                // acceptor library requests client session,
+                // the client sends one message to the acceptor
+                // library releases the session to the engine
+
+                logon(connection);
+                final long sessionId = fakeHandler.awaitSessionIdFor(INITIATOR_ID, ACCEPTOR_ID, () ->
+                    library.poll(2), 1000);
+                hasCompleted(library.requestSession(sessionId,
+                    0,
+                    0,
+                    2000L), ts);
+                // initiator sends a 35=8 to the acceptor
+                connection.sendExecutionReport(2, false);
+                connection.msgSeqNum(3);
+                ts.awaitMessageOf(fakeOtfAcceptor, "8");
+                // acceptor releases the session
+                hasCompleted(library.releaseToGateway(library.sessions().get(0), 1000), ts);
+
+
+
+                //////////// WHEN
+                // the library times out,
+                // the library reconnects,
+                // the library requests the same session from the engine
+
+                fakeOtfAcceptor.messages().clear();
+
+                // acceptor library times out and then reconnects
+                sleep(2000);
+                ts.await("library not timed out", () -> fakeHandler.isOnLibraryDisconnectCalled() == 1);
+                ts.await("library not timed out", () -> fakeHandler.isOnLibraryConnectCalled() == 2);
+                hasCompleted(library.requestSession(sessionId,
+                    0,
+                    0,
+                    2000L), ts);
+
+
+
+                //////////// THEN
+                // the acceptor library receives the 35=A twice (BUG) !!!!!
+
+                assertEquals(3, fakeOtfAcceptor.messages().size());
+                assertEquals("A", fakeOtfAcceptor.messages().get(0).msgType());
+                assertEquals("A", fakeOtfAcceptor.messages().get(1).msgType());
+                assertEquals("8", fakeOtfAcceptor.messages().get(2).msgType());
+
+
+                //////////// WHEN 2
+                // the requestSession is sent with seqno 2
+                hasCompleted(library.releaseToGateway(library.sessions().get(0), 1000), ts);
+                fakeOtfAcceptor.messages().clear();
+                sleep(2000);
+                ts.await("library not timed out", () -> fakeHandler.isOnLibraryDisconnectCalled() == 2);
+                ts.await("library not timed out", () -> fakeHandler.isOnLibraryConnectCalled() == 3);
+                hasCompleted(library.requestSession(sessionId,
+                    2,
+                    0,
+                    2000L), ts);
+
+                //////////// THEN
+                // it works fine
+                assertEquals(1, fakeOtfAcceptor.messages().size());
+                assertEquals("8", fakeOtfAcceptor.messages().get(0).msgType());
+
+
+            }
+        }
+
+    }
+
+    private static void hasCompleted(final Reply<SessionReplyStatus> sessionReplyStatusReply, final TestSystem ts)
+    {
+        ts.await("not received session " + sessionReplyStatusReply, sessionReplyStatusReply::hasCompleted);
+    }
+
     @Test(timeout = TEST_TIMEOUT_IN_MS)
     public void shouldRejectExceptionalLogonMessageAndLogout() throws IOException
     {
diff --git a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/SystemTestUtil.java b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/SystemTestUtil.java
index 8e4090174a..2832e0b8b5 100644
--- a/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/SystemTestUtil.java
+++ b/artio-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/SystemTestUtil.java
@@ -322,6 +322,7 @@ static LibraryConfiguration acceptingLibraryConfig(
         setupCommonConfig(ACCEPTOR_ID, INITIATOR_ID, nanoClock, libraryConfiguration);
 
         libraryConfiguration
+            .libraryConnectHandler(sessionHandler)
             .sessionExistsHandler(sessionHandler)
             .sessionAcquireHandler(sessionHandler)
             .libraryAeronChannels(singletonList(IPC_CHANNEL))