diff --git a/resources/install/scripts/app/ring_groups/index.lua b/resources/install/scripts/app/ring_groups/index.lua
index 6d4550bc59..b0b3045845 100644
--- a/resources/install/scripts/app/ring_groups/index.lua
+++ b/resources/install/scripts/app/ring_groups/index.lua
@@ -168,10 +168,10 @@
 
 --set the caller id
 	if (session:ready()) then
-		if (string.len(ring_group_cid_name_prefix) > 0) then
+		if (ring_group_cid_name_prefix ~= nil) then
 			session:execute("export", "effective_caller_id_name="..ring_group_cid_name_prefix.."#"..caller_id_name);
 		end
-		if (string.len(ring_group_cid_number_prefix) > 0) then
+		if (ring_group_cid_number_prefix ~= nil) then
 			session:execute("export", "effective_caller_id_number="..ring_group_cid_number_prefix..caller_id_number);
 		end
 	end