diff --git a/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferListTest.java b/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferListTest.java
new file mode 100644
index 0000000..c66e677
--- /dev/null
+++ b/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferListTest.java
@@ -0,0 +1,81 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.internal.tasks.core.externalization;
+
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+import org.eclipse.mylyn.internal.tasks.core.AbstractTask;
+import org.eclipse.mylyn.internal.tasks.core.ITransferList;
+import org.eclipse.mylyn.internal.tasks.core.TaskList;
+import org.eclipse.mylyn.internal.tasks.core.TaskTask;
+import org.junit.Before;
+import org.junit.Test;
+
+public class LazyTransferListTest {
+
+	private ITransferList taskList;
+
+	private LazyTransferList lazyList;
+
+	@Before
+	public void setUp() throws Exception {
+		taskList = mock(TaskList.class);
+		lazyList = new LazyTransferList(taskList);
+	}
+
+	@Test
+	public void addUnmatchedTask() {
+		AbstractTask task = spy(new TaskTask("kind", "repoUrl", "id"));
+
+		// add to unmatched
+		lazyList.addTask(task);
+
+		// should not add task to task list
+		verify(taskList, never()).addTask(task);
+		verify(taskList, never()).addTask(eq(task), any());
+
+		// commit should add the task to task list
+		lazyList.commit();
+		verify(taskList).addTask(task);
+
+		// subsequent commit should not add task again
+		lazyList.commit();
+		verifyNoMoreInteractions(taskList);
+	}
+
+	@Test
+	public void addSubTask() {
+		AbstractTask task = spy(new TaskTask("kind", "repoUrl", "parent"));
+		AbstractTask subTask = spy(new TaskTask("kind", "repoUrl", "child"));
+
+		// add subtask to a task container
+		lazyList.addTask(subTask);
+		lazyList.addTask(task);
+		lazyList.addTask(subTask, task);
+
+		// should add task and subtask to task list
+		verify(taskList).addTask(task);
+		verify(taskList).addTask(subTask, task);
+		verifyNoMoreInteractions(taskList);
+
+		// commit should not add anything to task list
+		lazyList.commit();
+		verifyNoMoreInteractions(taskList);
+	}
+
+}
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferList.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferList.java
new file mode 100644
index 0000000..a1a9604
--- /dev/null
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/LazyTransferList.java
@@ -0,0 +1,130 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.internal.tasks.core.externalization;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+import org.eclipse.mylyn.internal.tasks.core.AbstractTask;
+import org.eclipse.mylyn.internal.tasks.core.AbstractTaskCategory;
+import org.eclipse.mylyn.internal.tasks.core.AbstractTaskContainer;
+import org.eclipse.mylyn.internal.tasks.core.ITransferList;
+import org.eclipse.mylyn.internal.tasks.core.RepositoryQuery;
+import org.eclipse.mylyn.internal.tasks.core.TaskCategory;
+import org.eclipse.mylyn.internal.tasks.core.UnmatchedTaskContainer;
+import org.eclipse.mylyn.tasks.core.ITask;
+
+/**
+ * This class delegates the calls to underlying {@link ITransferList} while altering behavior of {@link #addTask(ITask)}
+ * and {@link #addTask(ITask, category)} methods to avoid adding tasks being loaded to task list's
+ * {@link UnmatchedTaskContainer} if they belong to a different task container. Instead, tasks added with
+ * {@link #addTask(ITask)} method are stored internally, and only pushed to underlying {@link ITransferList} during
+ * subsequent calls to {@link #addTask(ITask, category)} or on final {@link #commit(void)}.
+ * <p>
+ * <b>Usage</b>
+ * <p>
+ * The caller can call {@link #addTask(ITask)} and {@link #addTask(ITask, category)} methods to load task list as usual.
+ * <p>
+ * The caller is expected to call {@link #commit(void)} to add the remaining uncategorized tasks to task list.
+ *
+ * @see {@link #addTask(ITask)}
+ * @see {@link #addTask(ITask, AbstractTaskContainer)}
+ * @see {@link #commit()}
+ */
+class LazyTransferList implements ITransferList {
+
+	private final Map<String, ITask> untransferedTasks = new HashMap<>();
+
+	private final ITransferList taskList;
+
+	LazyTransferList(ITransferList taskList) {
+		this.taskList = taskList;
+	}
+
+	public void addCategory(TaskCategory category) {
+		taskList.addCategory(category);
+	}
+
+	public void addQuery(RepositoryQuery query) {
+		taskList.addQuery(query);
+	}
+
+	public void addTask(ITask task) {
+		untransferedTasks.put(task.getHandleIdentifier(), task);
+	}
+
+	public boolean addTask(ITask task, AbstractTaskContainer parentContainer) {
+		boolean result = taskList.addTask(task, commit(parentContainer));
+		untransferedTasks.remove(task.getHandleIdentifier());
+		return result;
+	}
+
+	public AbstractTaskCategory getContainerForHandle(String handle) {
+		return taskList.getContainerForHandle(handle);
+	}
+
+	public Collection<AbstractTask> getAllTasks() {
+		return taskList.getAllTasks();
+	}
+
+	public Set<AbstractTaskCategory> getCategories() {
+		return taskList.getCategories();
+	}
+
+	public Set<RepositoryQuery> getQueries() {
+		return taskList.getQueries();
+	}
+
+	public AbstractTask getTask(String handleIdentifier) {
+		AbstractTask task = (AbstractTask) untransferedTasks.get(handleIdentifier);
+
+		if (task == null) {
+			task = taskList.getTask(handleIdentifier);
+		}
+
+		return task;
+	}
+
+	public ITask getTask(String repositoryUrl, String taskId) {
+		return taskList.getTask(repositoryUrl, taskId);
+	}
+
+	/**
+	 * If the container is an {@link ITask}, pushes it to task list
+	 *
+	 * @param container
+	 */
+	private AbstractTaskContainer commit(AbstractTaskContainer container) {
+		if (container instanceof ITask) {
+			AbstractTask task = (AbstractTask) untransferedTasks.get(container.getHandleIdentifier());
+
+			if (task != null) {
+				taskList.addTask(task);
+				untransferedTasks.remove(container.getHandleIdentifier());
+			}
+		}
+
+		return container;
+	}
+
+	/**
+	 * Pushes the remaining tasks to task list
+	 */
+	public void commit() {
+		for (ITask task : untransferedTasks.values()) {
+			taskList.addTask(task);
+		}
+		untransferedTasks.clear();
+	}
+}
\ No newline at end of file
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/SaxTaskListHandler.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/SaxTaskListHandler.java
index 394d02e..7a1e38b 100644
--- a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/SaxTaskListHandler.java
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/externalization/SaxTaskListHandler.java
@@ -34,7 +34,7 @@
 
 public class SaxTaskListHandler extends DefaultHandler {
 
-	private final ITransferList taskList;
+	private final LazyTransferList taskList;
 
 	private final RepositoryModel repositoryModel;
 
@@ -52,7 +52,7 @@
 
 	public SaxTaskListHandler(ITransferList taskList, RepositoryModel repositoryModel,
 			IRepositoryManager repositoryManager) throws CoreException {
-		this.taskList = taskList;
+		this.taskList = new LazyTransferList(taskList);
 		this.repositoryModel = repositoryModel;
 		this.repositoryManager = repositoryManager;
 
@@ -151,7 +151,7 @@
 			applyContainmentToTaskList(subTasks);
 			applyContainmentToTaskList(queryResults);
 			applyContainmentToTaskList(categorizedTasks);
-
+			commitUntransferedTasksToTaskList();
 			break;
 		default:
 			break;
@@ -161,6 +161,10 @@
 
 	}
 
+	private void commitUntransferedTasksToTaskList() {
+		taskList.commit();
+	}
+
 	private <T extends IRepositoryElement> void recordHit(Attributes attributes, Multimap<T, String> hitMap,
 			SaxTaskListElementBuilder<T> builder) {
 		String handle = attributes.getValue(TaskListExternalizationConstants.KEY_HANDLE);