diff --git a/pitivi/timeline/elements.py b/pitivi/timeline/elements.py
index 6a47c26983b55e5b99b3aafb1ae22b780e7314ed..0f0905205fb839254bf56043ff44c1784ea99240 100644
--- a/pitivi/timeline/elements.py
+++ b/pitivi/timeline/elements.py
@@ -1596,6 +1596,14 @@ class TransitionClip(Clip):
 
         self.props.has_tooltip = True
 
+        overlay = self.get_children()[0]
+        assert isinstance(overlay, Gtk.Overlay)
+        drawing_area = Gtk.DrawingArea()
+        drawing_area.connect("draw", self._draw_cb)
+        overlay.add_overlay(drawing_area)
+        # Make this the lowermost layer to prevent it from blocking the trim handles.
+        overlay.reorder_overlay(drawing_area, 0)
+
     def do_query_tooltip(self, x, y, keyboard_mode, tooltip):
         if self.__has_video:
             markup = str(self.ges_clip.props.vtype.value_nick)
@@ -1605,6 +1613,25 @@ class TransitionClip(Clip):
 
         return True
 
+    def _draw_cb(self, unused_da, ctx):
+        height = self.ges_clip.ui.get_allocation().height
+        width = self.ges_clip.ui.get_allocation().width
+
+        # Draw triangle.
+        ctx.set_source_rgba(.5, .6, .8, .9)
+        ctx.move_to(0, height)
+        ctx.line_to(width, 0)
+        ctx.line_to(0, 0)
+        ctx.close_path()
+        ctx.fill()
+        # Highlight diagonal
+        ctx.new_path()
+        ctx.set_source_rgba(1, 1, 1, 1)
+        ctx.set_line_width(1)
+        ctx.move_to(0, height)
+        ctx.line_to(width, 0)
+        ctx.stroke()
+
     def _add_child(self, ges_timeline_element):
         Clip._add_child(self, ges_timeline_element)