diff --git a/src/cl.php b/src/cl.php
index 1144709..9e25be3 100644
--- a/src/cl.php
+++ b/src/cl.php
@@ -33,7 +33,9 @@ class cl {
    */
   static final function first(?iterable $iterable, $default=null) {
     if (is_array($iterable)) {
-      return $iterable[array_key_first($iterable)];
+      $key = array_key_first($iterable);
+      if ($key === null) return $default;
+      return $iterable[$key];
     }
     if (is_iterable($iterable)) {
       foreach ($iterable as $value) {
@@ -49,7 +51,9 @@ class cl {
    */
   static final function last(?iterable $iterable, $default=null) {
     if (is_array($iterable)) {
-      return $iterable[array_key_last($iterable)];
+      $key = array_key_last($iterable);
+      if ($key === null) return $default;
+      return $iterable[$key];
     }
     $value = $default;
     if (is_iterable($iterable)) {
diff --git a/src/db/CapacitorChannel.php b/src/db/CapacitorChannel.php
index d7846c6..0a38167 100644
--- a/src/db/CapacitorChannel.php
+++ b/src/db/CapacitorChannel.php
@@ -151,6 +151,7 @@ class CapacitorChannel {
     return $serial !== null? unserialize($serial): null;
   }
 
+  const SERIAL_DEFINITION = "mediumtext";
   const SUM_DEFINITION = "varchar(40)";
 
   final function sum(?string $serial, $value=null): ?string {
diff --git a/src/db/CapacitorStorage.php b/src/db/CapacitorStorage.php
index 5be8f83..7a2c4d6 100644
--- a/src/db/CapacitorStorage.php
+++ b/src/db/CapacitorStorage.php
@@ -30,7 +30,7 @@ abstract class CapacitorStorage {
   const PRIMARY_KEY_DEFINITION = null;
 
   const COLUMN_DEFINITIONS = [
-    "item__" => "text",
+    "item__" => CapacitorChannel::SERIAL_DEFINITION,
     "item__sum_" => CapacitorChannel::SUM_DEFINITION,
     "created_" => "datetime",
     "modified_" => "datetime",