diff --git a/ankiqt/ui/main.py b/ankiqt/ui/main.py
index 1e78ba68c..dcaa38552 100755
--- a/ankiqt/ui/main.py
+++ b/ankiqt/ui/main.py
@@ -2168,6 +2168,7 @@ it to your friends.
         self.connect(self.syncThread, SIGNAL("fullSyncFinished"), self.fullSyncFinished)
         self.connect(self.syncThread, SIGNAL("fullSyncProgress"), self.fullSyncProgress)
         self.connect(self.syncThread, SIGNAL("badUserPass"), self.badUserPass)
+        self.connect(self.syncThread, SIGNAL("syncConflicts"), self.onConflict)
         self.syncThread.start()
         self.switchToWelcomeScreen()
         self.setEnabled(False)
@@ -2185,6 +2186,22 @@ it to your friends.
                 ok.append(d)
         return ok
 
+    def onConflict(self, deckName):
+        diag = ui.utils.askUserDialog(_("""\
+<b>%s</b> has been changed on both the local<br>
+and remote side. What do you want to do?""" % deckName),
+                          [_("Keep Local"),
+                           _("Keep Remote"),
+                           _("Cancel")])
+        diag.setDefault(2)
+        ret = diag.run()
+        if ret == _("Keep Local"):
+            self.syncThread.conflictResolution = "keepLocal"
+        elif ret == _("Keep Remote"):
+            self.syncThread.conflictResolution = "keepRemote"
+        else:
+            self.syncThread.conflictResolution = "cancel"
+
     def onSyncFinished(self):
         "Reopen after sync finished."
         self.mainWin.buttonStack.show()
diff --git a/ankiqt/ui/sync.py b/ankiqt/ui/sync.py
index 1711d63e2..a7c88a63a 100755
--- a/ankiqt/ui/sync.py
+++ b/ankiqt/ui/sync.py
@@ -100,7 +100,8 @@ class Sync(QThread):
         # multi-mode setup
         if deck:
             c = sqlite.connect(deck)
-            syncName = c.execute("select syncName from decks").fetchone()[0]
+            (syncName, localChanged) = c.execute(
+                "select syncName, modified > lastSync from decks").fetchone()
             c.close()
             if not syncName:
                 return
@@ -108,6 +109,10 @@ class Sync(QThread):
         else:
             syncName = self.parent.syncName
             path = self.parent.deckPath
+            c = sqlite.connect(path)
+            localChanged = c.execute(
+                "select modified > lastSync from decks").fetchone()[0]
+            c.close()
         # ensure deck mods cached
         try:
             proxy = self.connect()
@@ -127,12 +132,25 @@ class Sync(QThread):
                 self.emit(SIGNAL("noMatchingDeck"), keys, not self.onlyMerge)
                 self.setStatus("")
                 return
-        self.setStatus(_("Syncing <b>%s</b>...") % syncName, 0)
+        # check clock
         timediff = abs(proxy.timestamp - time.time())
         if timediff > 300:
             self.emit(SIGNAL("syncClockOff"), timediff)
             return
+        # check conflicts
+        remoteChanged = proxy.hasChanged(syncName)
+        self.conflictResolution = None
+        if localChanged and remoteChanged:
+            self.emit(SIGNAL("syncConflicts"), syncName)
+            while not self.conflictResolution:
+                time.sleep(0.2)
+            if self.conflictResolution == "cancel":
+                if not deck:
+                    # alert we're finished early
+                    self.emit(SIGNAL("syncFinished"))
+                return
         # reopen
+        self.setStatus(_("Syncing <b>%s</b>...") % syncName, 0)
         self.deck = None
         try:
             self.deck = DeckStorage.Deck(path)
@@ -146,8 +164,12 @@ class Sync(QThread):
                 # summary
                 self.setStatus(_("Fetching summary from server..."), 0)
                 sums = client.summaries()
-                if client.needFullSync(sums):
+                if self.conflictResolution or client.needFullSync(sums):
                     self.setStatus(_("Preparing full sync..."), 0)
+                    if self.conflictResolution == "keepLocal":
+                        client.remoteTime = 0
+                    elif self.conflictResolution == "keepRemote":
+                        client.localTime = 0
                     ret = client.prepareFullSync()
                     if ret[0] == "fromLocal":
                         self.setStatus(_("Uploading..."), 0)
diff --git a/ankiqt/ui/utils.py b/ankiqt/ui/utils.py
index 1650e2522..094ad464e 100644
--- a/ankiqt/ui/utils.py
+++ b/ankiqt/ui/utils.py
@@ -75,6 +75,44 @@ def askUser(text, parent=None, help=""):
             break
     return r == QMessageBox.Yes
 
+class ButtonedDialog(QMessageBox):
+
+    def __init__(self, text, buttons, parent=None, help=""):
+        QDialog.__init__(self, parent)
+        self.buttons = []
+        self.setWindowTitle("Anki")
+        self.help = help
+        self.setIcon(QMessageBox.Warning)
+        self.setText(text)
+        # v = QVBoxLayout()
+        # v.addWidget(QLabel(text))
+        # box = QDialogButtonBox()
+        # v.addWidget(box)
+        for b in buttons:
+            self.buttons.append(
+                self.addButton(b, QMessageBox.AcceptRole))
+        if help:
+            self.addButton(_("Help"), QMessageBox.HelpRole)
+            buttons.append(_("Help"))
+        #self.setLayout(v)
+
+    def run(self):
+        self.exec_()
+        but = self.clickedButton().text()
+        if but == "Help":
+            # FIXME stop dialog closing?
+            openWikiLink(self.help)
+        return self.clickedButton().text()
+
+    def setDefault(self, idx):
+        self.setDefaultButton(self.buttons[idx])
+
+def askUserDialog(text, buttons, parent=None, help=""):
+    if not parent:
+        parent = ankiqt.mw
+    diag = ButtonedDialog(text, buttons, parent, help)
+    return diag
+
 class GetTextDialog(QDialog):
 
     def __init__(self, parent, question, help=None, edit=None):