diff --git a/src/ValueException.php b/src/ValueException.php
index 5f0ec3a..2c72f4f 100644
--- a/src/ValueException.php
+++ b/src/ValueException.php
@@ -44,8 +44,9 @@ class ValueException extends UserException {
     return new static(self::message(null, $message, $kind, $prefix, " should not be null"));
   }
 
-  static final function check_null($value, ?string $kind=null, ?string $prefix=null, ?string $message=null): void {
+  static final function check_null($value, ?string $kind=null, ?string $prefix=null, ?string $message=null) {
     if ($value === null) throw static::null($kind, $prefix, $message);
+    return $value;
   }
 
   static final function invalid_kind($value=null, ?string $kind=null, ?string $prefix=null, ?string $message=null): self {