diff --git a/REFERENCE.md b/REFERENCE.md
index 65d6955..8067dc9 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -135,11 +135,11 @@ Default value: `Integer(regsubst($title, '^\D+(\d+)$', '\1'))`
 
 ##### <a name="source_addresses"></a>`source_addresses`
 
-Data type: `Optional[Array[Stdlib::IP::Address]]`
+Data type: `Array[Stdlib::IP::Address]`
 
 an array of ip addresses from where we receive wireguard connections
 
-Default value: ``undef``
+Default value: `[]`
 
 ##### <a name="destination_addresses"></a>`destination_addresses`
 
diff --git a/manifests/interface.pp b/manifests/interface.pp
index 05fca94..b31eec9 100644
--- a/manifests/interface.pp
+++ b/manifests/interface.pp
@@ -38,7 +38,7 @@
   Integer[1024, 65000] $dport = Integer(regsubst($title, '^\D+(\d+)$', '\1')),
   Optional[String[1]] $input_interface = undef,
   Boolean $manage_firewall = true,
-  Optional[Array[Stdlib::IP::Address]] $source_addresses = undef,
+  Array[Stdlib::IP::Address] $source_addresses = [],
   Array[Hash[String,Variant[Stdlib::IP::Address::V4::CIDR,Stdlib::IP::Address::V6::CIDR]]] $addresses = [],
 ) {
   require wireguard