diff --git a/src/main/java/com/gitblit/wicket/pages/EditTicketPage.java b/src/main/java/com/gitblit/wicket/pages/EditTicketPage.java
index 61e1287..6b09062 100644
--- a/src/main/java/com/gitblit/wicket/pages/EditTicketPage.java
+++ b/src/main/java/com/gitblit/wicket/pages/EditTicketPage.java
@@ -42,6 +42,7 @@
 import com.gitblit.Constants.AccessPermission;
 import com.gitblit.Constants.AuthorizationControl;
 import com.gitblit.models.RegistrantAccessPermission;
+import com.gitblit.models.RepositoryModel;
 import com.gitblit.models.TicketModel;
 import com.gitblit.models.TicketModel.Change;
 import com.gitblit.models.TicketModel.Field;
@@ -152,7 +153,13 @@
 
 		form.setOutputMarkupId(true);
 
-		form.add(new TicketRelationEditorPanel("dependencies", dependenciesModel, getRepositoryModel()));
+		form.add(new TicketRelationEditorPanel("dependencies", dependenciesModel, ticket.number) {
+			private static final long serialVersionUID = 1L;
+			@Override
+			protected RepositoryModel getRepositoryModel() {
+				return EditTicketPage.this.getRepositoryModel();
+			}
+		});
 
 		final IModel<String> markdownPreviewModel = Model.of(ticket.body == null ? "" : ticket.body);
 		descriptionPreview = new Label("descriptionPreview", markdownPreviewModel);
diff --git a/src/main/java/com/gitblit/wicket/pages/NewTicketPage.java b/src/main/java/com/gitblit/wicket/pages/NewTicketPage.java
index 3722be1..011f4b6 100644
--- a/src/main/java/com/gitblit/wicket/pages/NewTicketPage.java
+++ b/src/main/java/com/gitblit/wicket/pages/NewTicketPage.java
@@ -39,6 +39,7 @@
 import com.gitblit.Constants.AccessPermission;
 import com.gitblit.Constants.AuthorizationControl;
 import com.gitblit.models.RegistrantAccessPermission;
+import com.gitblit.models.RepositoryModel;
 import com.gitblit.models.TicketModel;
 import com.gitblit.models.TicketModel.Change;
 import com.gitblit.models.TicketModel.Field;
@@ -127,7 +128,15 @@
 		descriptionEditor.setRepository(repositoryName);
 		form.add(descriptionEditor);
 		
-		form.add(new TicketRelationEditorPanel("dependencies", dependenciesModel, getRepositoryModel()));
+		form.add(new TicketRelationEditorPanel("dependencies", dependenciesModel,  null) {
+
+			private static final long serialVersionUID = 1L;
+			
+			@Override
+			protected RepositoryModel getRepositoryModel() {
+				return NewTicketPage.this.getRepositoryModel();
+			}
+		});
 
 		if (currentUser.canAdmin(null, getRepositoryModel())) {
 			// responsible
diff --git a/src/main/java/com/gitblit/wicket/panels/TicketRelationEditorPanel.java b/src/main/java/com/gitblit/wicket/panels/TicketRelationEditorPanel.java
index 59cc909..9b905c0 100644
--- a/src/main/java/com/gitblit/wicket/panels/TicketRelationEditorPanel.java
+++ b/src/main/java/com/gitblit/wicket/panels/TicketRelationEditorPanel.java
@@ -1,6 +1,8 @@
 package com.gitblit.wicket.panels;
 
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 import org.apache.wicket.PageParameters;
 import org.apache.wicket.ajax.AjaxRequestTarget;
@@ -14,21 +16,24 @@
 import org.jsoup.helper.StringUtil;
 
 import com.gitblit.models.RepositoryModel;
+import com.gitblit.models.TicketModel;
+import com.gitblit.tickets.ITicketService;
 import com.gitblit.wicket.WicketUtils;
 import com.gitblit.wicket.pages.TicketsPage;
 
-public class TicketRelationEditorPanel extends BasePanel {
+public abstract class TicketRelationEditorPanel extends BasePanel {
 
 	private static final long serialVersionUID = 1L;
 	
 	private IModel<List<String>> dependenciesModel;
 	private IModel<String> addDependencyModel;
-
+	private Long baseTicketId;
 	
-	public TicketRelationEditorPanel(String wicketId, IModel<List<String>> pdependenciesModel, final RepositoryModel repositoryModel) {
+	public TicketRelationEditorPanel(String wicketId, IModel<List<String>> pdependenciesModel, Long baseTicketId) {
 		super(wicketId);
 		this.dependenciesModel = pdependenciesModel;
 		this.addDependencyModel = Model.of();
+		this.baseTicketId = baseTicketId;
 		
 		
 		add(new ListView<String>("dependencyList", dependenciesModel) {
@@ -38,7 +43,7 @@
 			protected void populateItem(ListItem<String> item) {
 				final String ticketId = item.getModelObject();
 
-				PageParameters tp = WicketUtils.newObjectParameter(repositoryModel.name, ticketId);
+				PageParameters tp = WicketUtils.newObjectParameter(getRepositoryModel().name, ticketId);
 				item.add(new LinkPanel("dependencyLink", "list subject", "#"+ticketId, TicketsPage.class, tp));
 				
 				item.add(new AjaxButton("removeDependencyLink") {
@@ -60,23 +65,51 @@
 			protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
 				String ticketIdStr = addDependencyModel.getObject();
 				if (!StringUtil.isBlank(ticketIdStr)) {
-					try {
-						long ticketId = Long.parseLong(ticketIdStr);
-						if (app().tickets().hasTicket(repositoryModel, ticketId)) {
-							List<String> list = (List<String>) dependenciesModel.getObject();
-							list.add(String.valueOf(ticketId));
-							addDependencyModel.setObject("");
-						}
-					} catch (NumberFormatException e) {
-						// TODO : not allowed
-						
+					if (checkCycle(ticketIdStr)) {
+						List<String> list = (List<String>) dependenciesModel.getObject();
+						list.add(ticketIdStr.trim());
+						addDependencyModel.setObject("");
 					}
 				}
 				target.addComponent(form);
 			}
 		});
-		
-		
 	}
+	
+	private boolean checkCycle(String ticketId) {
+		Set<Long> tickets = new HashSet<Long>();
+		if (baseTicketId != null) {
+			tickets.add(baseTicketId);
+		}
+		return checkCycle(tickets, ticketId);
+	}
+
+	private boolean checkCycle(Set<Long> tickets, String ticketIdStr) {
+		try {
+			long ticketId = Long.parseLong(ticketIdStr);
+			if (tickets.contains(ticketId)) {
+				return false;
+			}
+			ITicketService ticketService = app().tickets();
+			RepositoryModel r = getRepositoryModel();
+			if (ticketService.hasTicket(r, ticketId)) {
+				TicketModel ticket = ticketService.getTicket(r, ticketId);
+				tickets.add(ticketId);
+				for (String subTicketIdStr : ticket.getDependencies()) {
+					if (!checkCycle(tickets, subTicketIdStr)) {
+						return false;
+					}
+				}
+				tickets.remove(ticketId);
+				return true;
+			} else {
+				return false;
+			}
+		} catch (NumberFormatException e) {
+			return false;
+		}
+	}	
+	
+	protected abstract RepositoryModel getRepositoryModel();
 
 }