diff --git a/data/ui/source-dialog.ui b/data/ui/source-dialog.ui
index 91f46c18..27528b0f 100644
--- a/data/ui/source-dialog.ui
+++ b/data/ui/source-dialog.ui
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- Generated with glade 3.18.1 -->
 <interface>
-  <requires lib="gtk+" version="3.16"/>
+  <requires lib="gtk+" version="3.15"/>
   <template class="GcalSourceDialog" parent="GtkDialog">
     <property name="can_focus">False</property>
     <property name="type_hint">dialog</property>