diff --git a/gui/source.py b/gui/source.py
index 9f9e7f8..3a57562 100644
--- a/gui/source.py
+++ b/gui/source.py
@@ -147,6 +147,8 @@ class SourceWindow:
         self.do_step = Invoker("step")
         self.do_next = Invoker("next")
         self.do_continue = Invoker("continue")
+        self.do_finish = Invoker("finish")
+        self.do_stop = Invoker("interrupt")
 
         builder = Gtk.Builder()
         builder.add_from_file(os.path.join(gui.self_dir, 'sourcewindow.xml'))
@@ -159,10 +161,6 @@ class SourceWindow:
 
         self.window.show()
 
-    def do_stop(self, *args):
-        # FIXME.
-        pass
-
     def deleted(self, widget, event):
         lru_handler.remove(self)
 
diff --git a/gui/sourcewindow.xml b/gui/sourcewindow.xml
index 635e8ed..9067566 100644
--- a/gui/sourcewindow.xml
+++ b/gui/sourcewindow.xml
@@ -17,6 +17,11 @@
     <property name="can_focus">False</property>
     <property name="pixbuf">icons/step-into.xpm</property>
   </object>
+  <object class="GtkImage" id="image4">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="pixbuf">icons/step-out.xpm</property>
+  </object>
   <object class="GtkWindow" id="sourcewindow">
     <property name="can_focus">False</property>
     <property name="title" translatable="yes">Source</property>
@@ -95,6 +100,20 @@
                 <property name="homogeneous">True</property>
               </packing>
             </child>
+            <child>
+              <object class="GtkToolButton" id="finish">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="tooltip_text" translatable="yes">Run until the current function returns</property>
+                <property name="label" translatable="yes">Finish</property>
+                <property name="use_underline">True</property>
+                <property name="icon_widget">image4</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="homogeneous">True</property>
+              </packing>
+            </child>
           </object>
           <packing>
             <property name="expand">False</property>