diff --git a/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/ActiveSession.java b/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/ActiveSession.java
index 233380b6c..77ca82f26 100644
--- a/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/ActiveSession.java
+++ b/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/ActiveSession.java
@@ -56,7 +56,7 @@ public class ActiveSession {
     }
 
     public FinishedSession toFinishedSession(long end) {
-        return new FinishedSession(playerUUID, serverUUID, start, end, afkTime, extraData);
+        return new FinishedSession(playerUUID, serverUUID, start, end, afkTime, extraData.copy());
     }
 
     public UUID getPlayerUUID() {
diff --git a/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/DataMap.java b/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/DataMap.java
index 5cd51803d..6f17595d3 100644
--- a/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/DataMap.java
+++ b/Plan/common/src/main/java/com/djrapitops/plan/gathering/domain/DataMap.java
@@ -29,6 +29,10 @@ public class DataMap {
         this.data = new HashMap<>();
     }
 
+    private DataMap(Map<String, Object> data) {
+        this.data = new HashMap<>(data);
+    }
+
     public <T> void put(Class<T> type, T value) {
         data.put(type.getName(), value);
     }
@@ -57,4 +61,8 @@ public class DataMap {
                 "data=" + data +
                 '}';
     }
+
+    public DataMap copy() {
+        return new DataMap(data);
+    }
 }
diff --git a/Plan/common/src/test/java/com/djrapitops/plan/gathering/domain/ActiveSessionTest.java b/Plan/common/src/test/java/com/djrapitops/plan/gathering/domain/ActiveSessionTest.java
new file mode 100644
index 000000000..1ac8b125b
--- /dev/null
+++ b/Plan/common/src/test/java/com/djrapitops/plan/gathering/domain/ActiveSessionTest.java
@@ -0,0 +1,35 @@
+/*
+ *  This file is part of Player Analytics (Plan).
+ *
+ *  Plan is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Lesser General Public License v3 as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Plan is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with Plan. If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.djrapitops.plan.gathering.domain;
+
+import org.junit.jupiter.api.Test;
+import utilities.RandomData;
+import utilities.TestConstants;
+
+class ActiveSessionTest {
+
+    @Test
+    void noStackOverflowErrorFromFinishingSession() {
+        ActiveSession session = RandomData.randomUnfinishedSession(TestConstants.SERVER_UUID, TestConstants.WORLDS, TestConstants.PLAYER_ONE_UUID, TestConstants.PLAYER_TWO_UUID);
+
+        FinishedSession finishedSession = session.toFinishedSession(System.currentTimeMillis());
+
+        session.hashCode(); // Error was here
+        finishedSession.hashCode();
+    }
+
+}
\ No newline at end of file
diff --git a/Plan/common/src/test/java/utilities/TestConstants.java b/Plan/common/src/test/java/utilities/TestConstants.java
index 6cd9cc167..3824a1e16 100644
--- a/Plan/common/src/test/java/utilities/TestConstants.java
+++ b/Plan/common/src/test/java/utilities/TestConstants.java
@@ -28,6 +28,7 @@ import java.util.function.Supplier;
  */
 public class TestConstants {
 
+
     private TestConstants() {
         /* Static variable class */
     }
@@ -47,6 +48,7 @@ public class TestConstants {
     public static final Supplier<String> PLAYER_HOSTNAME = () -> "play.example.com";
 
     public static final String WORLD_ONE_NAME = "World One";
+    public static final String[] WORLDS = new String[]{WORLD_ONE_NAME};
     public static final Long REGISTER_TIME = RandomData.randomTime();
 
     public static final int SERVER_MAX_PLAYERS = 20;