diff --git a/docs/Uppercase.md b/docs/Uppercase.md
index 0c7e80de..c1039d59 100644
--- a/docs/Uppercase.md
+++ b/docs/Uppercase.md
@@ -2,10 +2,20 @@
 
 - `Uppercase()`
 
-Validates if string characters are uppercase in the input:
+Validates whether the characters in the input are uppercase.
 
 ```php
-v::stringType()->uppercase()->validate('W3C'); // true
+v::uppercase()->validate('W3C'); // true
+```
+
+This rule does not validate if the input a numeric value, so `123` and `%` will
+be valid. Please add more validations to the chain if you want to refine your
+validation.
+
+```php
+v::not(v::numericVal())->uppercase()->validate('42'); // false
+v::alnum()->uppercase()->validate('#$%!'); // false
+v::not(v::numericVal())->alnum()->uppercase()->validate('W3C'); // true
 ```
 
 ## Changelog
@@ -17,4 +27,6 @@ Version | Description
 ***
 See also:
 
+- [Alnum](Alnum.md)
 - [Lowercase](Lowercase.md)
+- [NumericVal](NumericVal.md)
diff --git a/library/Exceptions/UppercaseException.php b/library/Exceptions/UppercaseException.php
index b1bcddda..3fe1b9a3 100644
--- a/library/Exceptions/UppercaseException.php
+++ b/library/Exceptions/UppercaseException.php
@@ -13,8 +13,16 @@ declare(strict_types=1);
 
 namespace Respect\Validation\Exceptions;
 
-class UppercaseException extends ValidationException
+/**
+ * @author Danilo Benevides <danilobenevides01@gmail.com>
+ * @author Henrique Moody <henriquemoody@gmail.com>
+ * @author Jean Pimentel <jeanfap@gmail.com>
+ */
+final class UppercaseException extends ValidationException
 {
+    /**
+     * {@inheritdoc}
+     */
     public static $defaultTemplates = [
         self::MODE_DEFAULT => [
             self::STANDARD => '{{name}} must be uppercase',
diff --git a/library/Rules/Uppercase.php b/library/Rules/Uppercase.php
index 6372f6ba..3716292e 100644
--- a/library/Rules/Uppercase.php
+++ b/library/Rules/Uppercase.php
@@ -13,10 +13,29 @@ declare(strict_types=1);
 
 namespace Respect\Validation\Rules;
 
-class Uppercase extends AbstractRule
+use function is_string;
+use function mb_detect_encoding;
+use function mb_strtoupper;
+
+/**
+ * Validates whether the characters in the input are uppercase.
+ *
+ * @author Alexandre Gomes Gaigalas <alexandre@gaigalas.net>
+ * @author Danilo Benevides <danilobenevides01@gmail.com>
+ * @author Henrique Moody <henriquemoody@gmail.com>
+ * @author Jean Pimentel <jeanfap@gmail.com>
+ */
+final class Uppercase extends AbstractRule
 {
+    /**
+     * {@inheritdoc}
+     */
     public function validate($input): bool
     {
+        if (!is_string($input)) {
+            return false;
+        }
+
         return $input === mb_strtoupper($input, mb_detect_encoding($input));
     }
 }
diff --git a/tests/integration/rules/uppercase.phpt b/tests/integration/rules/uppercase.phpt
new file mode 100644
index 00000000..cdd17521
--- /dev/null
+++ b/tests/integration/rules/uppercase.phpt
@@ -0,0 +1,38 @@
+--FILE--
+<?php
+require 'vendor/autoload.php';
+
+use Respect\Validation\Exceptions\NestedValidationException;
+use Respect\Validation\Exceptions\UppercaseException;
+use Respect\Validation\Validator as v;
+
+try {
+    v::uppercase()->check('lowercase');
+} catch (UppercaseException $exception) {
+    echo $exception->getMessage().PHP_EOL;
+}
+
+try {
+    v::uppercase()->assert('lowercase');
+} catch (NestedValidationException $exception) {
+    echo $exception->getFullMessage().PHP_EOL;
+}
+
+try {
+    v::not(v::uppercase())->check('UPPERCASE');
+} catch (UppercaseException $exception) {
+    echo $exception->getMessage().PHP_EOL;
+}
+
+try {
+    v::not(v::uppercase())->assert('UPPERCASE');
+} catch (NestedValidationException $exception) {
+    echo $exception->getFullMessage().PHP_EOL;
+}
+
+?>
+--EXPECTF--
+"lowercase" must be uppercase
+- "lowercase" must be uppercase
+"UPPERCASE" must not be uppercase
+- "UPPERCASE" must not be uppercase
diff --git a/tests/unit/Rules/UppercaseTest.php b/tests/unit/Rules/UppercaseTest.php
index d28ef306..e6b337e4 100644
--- a/tests/unit/Rules/UppercaseTest.php
+++ b/tests/unit/Rules/UppercaseTest.php
@@ -13,58 +13,58 @@ declare(strict_types=1);
 
 namespace Respect\Validation\Rules;
 
-use PHPUnit\Framework\TestCase;
+use Respect\Validation\Test\RuleTestCase;
+use stdClass;
 
 /**
- * @group  rule
+ * @group rule
+ *
  * @covers \Respect\Validation\Rules\Uppercase
- * @covers \Respect\Validation\Exceptions\UppercaseException
+ *
+ * @author Danilo Benevides <danilobenevides01@gmail.com>
+ * @author Gabriel Caruso <carusogabriel34@gmail.com>
+ * @author Henrique Moody <henriquemoody@gmail.com>
+ * @author Jean Pimentel <jeanfap@gmail.com>
  */
-class UppercaseTest extends TestCase
+final class UppercaseTest extends RuleTestCase
 {
-    /**
-     * @dataProvider providerForValidUppercase
-     */
-    public function testValidUppercaseShouldReturnTrue($input): void
+    /*
+    * {@inheritdoc}
+    */
+    public function providerForValidInput(): array
     {
-        $uppercase = new Uppercase();
-        self::assertTrue($uppercase->validate($input));
-        $uppercase->assert($input);
-        $uppercase->check($input);
-    }
+        $rule = new Uppercase();
 
-    /**
-     * @dataProvider providerForInvalidUppercase
-     * @expectedException \Respect\Validation\Exceptions\UppercaseException
-     */
-    public function testInvalidUppercaseShouldThrowException($input): void
-    {
-        $lowercase = new Uppercase();
-        self::assertFalse($lowercase->validate($input));
-        $lowercase->assert($input);
-    }
-
-    public function providerForValidUppercase()
-    {
         return [
-            [''],
-            ['UPPERCASE'],
-            ['UPPERCASE-WITH-DASHES'],
-            ['UPPERCASE WITH SPACES'],
-            ['UPPERCASE WITH NUMBERS 123'],
-            ['UPPERCASE WITH SPECIALS CHARACTERS LIKE Ã Ç Ê'],
-            ['WITH SPECIALS CHARACTERS LIKE # $ % & * +'],
-            ['ΤΆΧΙΣΤΗ ΑΛΏΠΗΞ ΒΑΦΉΣ ΨΗΜΈΝΗ ΓΗ, ΔΡΑΣΚΕΛΊΖΕΙ ΥΠΈΡ ΝΩΘΡΟΎ ΚΥΝΌΣ'],
+            [$rule, ''],
+            [$rule, 'UPPERCASE'],
+            [$rule, 'UPPERCASE-WITH-DASHES'],
+            [$rule, 'UPPERCASE WITH SPACES'],
+            [$rule, 'UPPERCASE WITH NUMBERS 123'],
+            [$rule, 'UPPERCASE WITH SPECIALS CHARACTERS LIKE Ã Ç Ê'],
+            [$rule, 'WITH SPECIALS CHARACTERS LIKE # $ % & * +'],
+            [$rule, 'ΤΆΧΙΣΤΗ ΑΛΏΠΗΞ ΒΑΦΉΣ ΨΗΜΈΝΗ ΓΗ, ΔΡΑΣΚΕΛΊΖΕΙ ΥΠΈΡ ΝΩΘΡΟΎ ΚΥΝΌΣ'],
+            // Uppercase should not restrict these
+            [$rule, '42'],
+            [$rule, '!@#$%^'],
         ];
     }
 
-    public function providerForInvalidUppercase()
+    /*
+    * {@inheritdoc}
+    */
+    public function providerForInvalidInput(): array
     {
+        $rule = new Uppercase();
+
         return [
-            ['lowercase'],
-            ['CamelCase'],
-            ['First Character Uppercase'],
-            ['With Numbers 1 2 3'],
+            [$rule, 42],
+            [$rule, []],
+            [$rule, new stdClass()],
+            [$rule, 'lowercase'],
+            [$rule, 'CamelCase'],
+            [$rule, 'First Character Uppercase'],
+            [$rule, 'With Numbers 1 2 3'],
         ];
     }
 }