diff --git a/admin/src/Table/AllowTable.php b/admin/src/Table/AllowTable.php
index 00af5bf..d63ecc6 100644
--- a/admin/src/Table/AllowTable.php
+++ b/admin/src/Table/AllowTable.php
@@ -10,6 +10,7 @@
 
 defined('_JEXEC') or die;
 
+use Codeling\Plugin\System\Bfstop\Helper\IpHelper;
 use Joomla\CMS\Table\Table;
 use Joomla\Database\DatabaseDriver;
 
@@ -30,6 +31,14 @@ public function check()
 		{
 			$this->id = 0;
 		}
+		// addresses and networks are looked up by their canonical spelling, see
+		// IpHelper::canonicalEntry() ("2001:DB8::1" and "203.0.113.5/24" are
+		// kept as "2001:db8::1" and "203.0.113.0/24")
+		$canonical = IpHelper::canonicalEntry($this->ipaddress);
+		if ($canonical !== null)
+		{
+			$this->ipaddress = $canonical;
+		}
 		return parent::check();
 	}
 }
diff --git a/admin/src/Table/BlockTable.php b/admin/src/Table/BlockTable.php
index 0f6668f..0301094 100644
--- a/admin/src/Table/BlockTable.php
+++ b/admin/src/Table/BlockTable.php
@@ -10,6 +10,7 @@
 
 defined('_JEXEC') or die;
 
+use Codeling\Plugin\System\Bfstop\Helper\IpHelper;
 use Joomla\CMS\Table\Table;
 use Joomla\Database\DatabaseDriver;
 
@@ -30,6 +31,14 @@ public function check()
 		{
 			$this->id = 0;
 		}
+		// addresses and networks are looked up by their canonical spelling, see
+		// IpHelper::canonicalEntry() ("2001:DB8::1" and "203.0.113.5/24" are
+		// kept as "2001:db8::1" and "203.0.113.0/24")
+		$canonical = IpHelper::canonicalEntry($this->ipaddress);
+		if ($canonical !== null)
+		{
+			$this->ipaddress = $canonical;
+		}
 		return parent::check();
 	}
 }