diff --git a/data/key-mapper.glade b/data/key-mapper.glade
index 6ec429cf..95660bcd 100644
--- a/data/key-mapper.glade
+++ b/data/key-mapper.glade
@@ -356,6 +356,20 @@
                 <property name="position">1</property>
               </packing>
             </child>
+            <child>
+              <object class="GtkSeparator">
+                <property name="visible">True</property>
+                <property name="can-focus">False</property>
+                <style>
+                  <class name="top_separator"/>
+                </style>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="position">2</property>
+              </packing>
+            </child>
             <style>
               <class name="primary-toolbar"/>
             </style>
diff --git a/data/style.css b/data/style.css
index bad33d91..bb96648e 100644
--- a/data/style.css
+++ b/data/style.css
@@ -7,6 +7,13 @@ row {
     border: 0px;
 }
 
+/* adds a bottom border for themes that don't add one in primary-toolbar
+classes. Interestingly, those that do add a border ignore this separator,
+which is perfect. */
+.top_separator {
+    border: 0px; /* fixes light pixels on each end in arc-dark */
+}
+
 .table-header, .row-box {
     padding: 2px;
 }