diff --git a/src/Model/CreatePaymentCustomer.php b/src/Model/CreatePaymentCustomer.php
index 205a97f..8446a4d 100644
--- a/src/Model/CreatePaymentCustomer.php
+++ b/src/Model/CreatePaymentCustomer.php
@@ -3,16 +3,17 @@
 namespace ThePay\ApiClient\Model;
 
 use InvalidArgumentException;
+use ThePay\ApiClient\ValueObject\EmailAddress;
+use ThePay\ApiClient\ValueObject\NonEmptyString;
 use ThePay\ApiClient\ValueObject\PhoneNumber;
-use ThePay\ApiClient\ValueObject\StringValue;
 
 final class CreatePaymentCustomer
 {
     private string $name;
     private string $surname;
-    /** @var StringValue|null */
+    /** @var string|null */
     private $email;
-    /** @var PhoneNumber|null */
+    /** @var string|null */
     private $phone;
     /** @var Address|null */
     private $billingAddress;
@@ -31,10 +32,10 @@ public function __construct(string $name, string $surname, $email, $phone, Addre
             throw new InvalidArgumentException('At least one of $email and $phone is required.');
         }
 
-        $this->name = $name;
-        $this->surname = $surname;
-        $this->email = $email === null ? null : new StringValue($email);
-        $this->phone = $phone === null ? null : new PhoneNumber($phone);
+        $this->name = (new NonEmptyString($name))->getValue();
+        $this->surname = (new NonEmptyString($surname))->getValue();
+        $this->email = $email === null ? null : (new EmailAddress($email))->getValue();
+        $this->phone = $phone === null ? null : (new PhoneNumber($phone))->getValue();
         $this->billingAddress = $billingAddress;
         $this->shippingAddress = $shippingAddress;
     }
@@ -54,7 +55,7 @@ public function getSurname(): string
      */
     public function getEmail()
     {
-        return $this->email === null ? null : $this->email->getValue();
+        return $this->email;
     }
 
     /**
@@ -62,7 +63,7 @@ public function getEmail()
      */
     public function getPhone()
     {
-        return $this->phone === null ? null : $this->phone->getValue();
+        return $this->phone;
     }
 
     /**
diff --git a/src/ValueObject/Amount.php b/src/ValueObject/Amount.php
index 1056318..5d7d71a 100644
--- a/src/ValueObject/Amount.php
+++ b/src/ValueObject/Amount.php
@@ -4,11 +4,11 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<int>
+ */
 final class Amount extends BaseValueObject
 {
-    /** @var int */
-    private $value;
-
     /**
      * Amount constructor.
      *
diff --git a/src/ValueObject/BaseValueObject.php b/src/ValueObject/BaseValueObject.php
index e4440eb..f660840 100644
--- a/src/ValueObject/BaseValueObject.php
+++ b/src/ValueObject/BaseValueObject.php
@@ -2,13 +2,27 @@
 
 namespace ThePay\ApiClient\ValueObject;
 
+use InvalidArgumentException;
+
+/**
+ * @template TValue of mixed
+ */
 abstract class BaseValueObject implements ValueObject
 {
     /**
-     * BaseValueObject constructor.
-     * @param mixed $value
+     * @var TValue
      */
-    abstract public function __construct($value);
+    protected $value;
+
+    /**
+     * @param TValue|mixed $value
+     *
+     * @throws InvalidArgumentException
+     */
+    final public function __construct($value)
+    {
+        $this->value = static::filter($value);
+    }
 
     /**
      * @param mixed $value
@@ -30,4 +44,34 @@ public function equals(ValueObject $object)
 
         return $this->getValue() === $object->getValue();
     }
+
+
+    /**
+     * @return TValue
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+
+    /**
+     * @internal should be abstract
+     *
+     * @param TValue|mixed $value
+     *
+     * @return TValue
+     *
+     * @throws InvalidArgumentException
+     */
+    protected static function filter($value)
+    {
+        throw self::invalidValue('expected');
+    }
+
+    protected static function invalidValue(string $expected, ?string $actual = null): InvalidArgumentException
+    {
+        return new InvalidArgumentException(
+            'Value ' . ($actual === null ? '' : '"' . $actual . '" ') . 'is not ' . $expected,
+        );
+    }
 }
diff --git a/src/ValueObject/CountryCode.php b/src/ValueObject/CountryCode.php
index dc9275e..9fad216 100644
--- a/src/ValueObject/CountryCode.php
+++ b/src/ValueObject/CountryCode.php
@@ -2,11 +2,11 @@
 
 namespace ThePay\ApiClient\ValueObject;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class CountryCode extends BaseValueObject
 {
-    /** @var string */
-    private $value;
-
     /**
      * @param string $value
      */
diff --git a/src/ValueObject/CurrencyCode.php b/src/ValueObject/CurrencyCode.php
index 653de62..5276f78 100644
--- a/src/ValueObject/CurrencyCode.php
+++ b/src/ValueObject/CurrencyCode.php
@@ -4,11 +4,11 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class CurrencyCode extends BaseValueObject
 {
-    /** @var string */
-    private $value;
-
     /**
      * CurrencyCode constructor.
      *
diff --git a/src/ValueObject/EmailAddress.php b/src/ValueObject/EmailAddress.php
new file mode 100644
index 0000000..7fa515b
--- /dev/null
+++ b/src/ValueObject/EmailAddress.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace ThePay\ApiClient\ValueObject;
+
+class EmailAddress extends NonEmptyString
+{
+    public static function filter($value)
+    {
+        $nonEmptyString = parent::filter($value);
+        $emailAddress = filter_var($nonEmptyString, FILTER_VALIDATE_EMAIL);
+
+        if ($emailAddress === false) {
+            throw self::invalidValue('e-mail address', $nonEmptyString);
+        }
+        return $emailAddress;
+    }
+}
diff --git a/src/ValueObject/EnumValueObject.php b/src/ValueObject/EnumValueObject.php
index 529c0c8..a12e831 100644
--- a/src/ValueObject/EnumValueObject.php
+++ b/src/ValueObject/EnumValueObject.php
@@ -2,11 +2,11 @@
 
 namespace ThePay\ApiClient\ValueObject;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 abstract class EnumValueObject extends BaseValueObject
 {
-    /** @var string */
-    protected $value;
-
     /**
      * @param string $value
      */
diff --git a/src/ValueObject/Identifier.php b/src/ValueObject/Identifier.php
index ed86a22..ee77934 100644
--- a/src/ValueObject/Identifier.php
+++ b/src/ValueObject/Identifier.php
@@ -4,11 +4,11 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class Identifier extends BaseValueObject
 {
-    /** @var string */
-    private $value;
-
     /**
      * Uid constructor.
      *
diff --git a/src/ValueObject/LanguageCode.php b/src/ValueObject/LanguageCode.php
index f384464..6a5348a 100644
--- a/src/ValueObject/LanguageCode.php
+++ b/src/ValueObject/LanguageCode.php
@@ -4,11 +4,11 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class LanguageCode extends BaseValueObject
 {
-    /** @var string */
-    private $value;
-
     /**
      * CurrencyCode constructor.
      *
diff --git a/src/ValueObject/NonEmptyString.php b/src/ValueObject/NonEmptyString.php
new file mode 100644
index 0000000..6e54759
--- /dev/null
+++ b/src/ValueObject/NonEmptyString.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace ThePay\ApiClient\ValueObject;
+
+class NonEmptyString extends StringValue
+{
+    protected static function filter($value)
+    {
+        $string = parent::filter($value);
+
+        if (trim($string) === '') {
+            throw self::invalidValue('non-empty string', $string);
+        }
+
+        return $string;
+    }
+}
diff --git a/src/ValueObject/PhoneNumber.php b/src/ValueObject/PhoneNumber.php
index 311d9f2..ba94ecd 100644
--- a/src/ValueObject/PhoneNumber.php
+++ b/src/ValueObject/PhoneNumber.php
@@ -4,6 +4,9 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class PhoneNumber extends BaseValueObject
 {
     /** @var string */
diff --git a/src/ValueObject/SecureUrl.php b/src/ValueObject/SecureUrl.php
index ed9ff78..9193d0a 100644
--- a/src/ValueObject/SecureUrl.php
+++ b/src/ValueObject/SecureUrl.php
@@ -2,6 +2,9 @@
 
 namespace ThePay\ApiClient\ValueObject;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class SecureUrl extends BaseValueObject
 {
     /** @var string */
diff --git a/src/ValueObject/StringValue.php b/src/ValueObject/StringValue.php
index da0401a..50443bb 100644
--- a/src/ValueObject/StringValue.php
+++ b/src/ValueObject/StringValue.php
@@ -2,33 +2,22 @@
 
 namespace ThePay\ApiClient\ValueObject;
 
-final class StringValue extends BaseValueObject
+/**
+ * @extends BaseValueObject<string>
+ */
+class StringValue extends BaseValueObject
 {
-    /** @var string */
-    private $value;
-
-    public function __construct($value)
-    {
-        if ( ! is_string($value)) {
-            throw new \InvalidArgumentException('type of value: ' . (string) $value . ' is not string');
-        }
-
-        $this->value = $value;
-    }
-
-    /**
-     * @return string
-     */
     public function __toString()
     {
         return $this->value;
     }
 
-    /**
-     * @return string
-     */
-    public function getValue()
+    protected static function filter($value)
     {
-        return $this->value;
+        if ( ! is_string($value)) {
+            throw self::invalidValue('string');
+        }
+
+        return $value;
     }
 }
diff --git a/src/ValueObject/Url.php b/src/ValueObject/Url.php
index dc6d970..cb5831c 100644
--- a/src/ValueObject/Url.php
+++ b/src/ValueObject/Url.php
@@ -4,6 +4,9 @@
 
 use InvalidArgumentException;
 
+/**
+ * @extends BaseValueObject<string>
+ */
 final class Url extends BaseValueObject
 {
     /** @var string */
diff --git a/src/ValueObject/ValueObject.php b/src/ValueObject/ValueObject.php
index 00ba024..c93e893 100644
--- a/src/ValueObject/ValueObject.php
+++ b/src/ValueObject/ValueObject.php
@@ -4,11 +4,6 @@
 
 interface ValueObject
 {
-    /**
-     * @param mixed $value
-     */
-    public function __construct($value);
-
     /**
      * @return string
      */