diff --git a/res-common/values/integers.xml b/res-common/values/integers.xml
index 2659f14..857a89f 100644
--- a/res-common/values/integers.xml
+++ b/res-common/values/integers.xml
@@ -36,4 +36,7 @@
 
     <!-- A big number to make sure "About contacts" always showing at the bottom of Settings.-->
     <integer name="about_contacts_order_number">100</integer>
+
+    <!-- The minimum number of contacts required before the alphabetic index is displayed. -->
+    <integer name="min_contacts_for_alphabetic_index">30</integer>
 </resources>