diff --git a/src/Illuminate/Validation/Concerns/ValidatesAttributes.php b/src/Illuminate/Validation/Concerns/ValidatesAttributes.php
index 6d03629207d5..1f60e150061f 100644
--- a/src/Illuminate/Validation/Concerns/ValidatesAttributes.php
+++ b/src/Illuminate/Validation/Concerns/ValidatesAttributes.php
@@ -493,7 +493,7 @@ public function validateBoolean($attribute, $value, $parameters)
     {
         $acceptable = [true, false, 0, 1, '0', '1'];
 
-        if (($parameters[0] ?? null) === 'strict') {
+        if (isset($parameters[0]) && strtolower($parameters[0]) === 'strict') {
             $acceptable = [true, false];
         }
 
diff --git a/tests/Validation/ValidationValidatorTest.php b/tests/Validation/ValidationValidatorTest.php
index f5c76189b153..a556c96035ab 100755
--- a/tests/Validation/ValidationValidatorTest.php
+++ b/tests/Validation/ValidationValidatorTest.php
@@ -3154,6 +3154,44 @@ public function testValidateBooleanStrict()
         $this->assertFalse($v->passes());
     }
 
+    public function testValidateBooleanStrictWithUpperCase()
+    {
+        $trans = $this->getIlluminateArrayTranslator();
+
+        $v = new Validator($trans, ['foo' => false], ['foo' => 'Boolean:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => true], ['foo' => 'Boolean:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'no'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'yes'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'false'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'true'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, [], ['foo' => 'Boolean:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => '1'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 1], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => '0'], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 0], ['foo' => 'Boolean:STRICT']);
+        $this->assertFalse($v->passes());
+    }
+
     public function testValidateBool()
     {
         $trans = $this->getIlluminateArrayTranslator();
@@ -3229,6 +3267,44 @@ public function testValidateBoolStrict()
         $this->assertFalse($v->passes());
     }
 
+    public function testValidateBoolStrictWithUpperCase()
+    {
+        $trans = $this->getIlluminateArrayTranslator();
+
+        $v = new Validator($trans, ['foo' => false], ['foo' => 'Bool:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => true], ['foo' => 'Bool:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'no'], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'yes'], ['foo' => 'Bool']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'false'], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 'true'], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, [], ['foo' => 'Bool:STRICT']);
+        $this->assertTrue($v->passes());
+
+        $v = new Validator($trans, ['foo' => '1'], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 1], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => '0'], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+
+        $v = new Validator($trans, ['foo' => 0], ['foo' => 'Bool:STRICT']);
+        $this->assertFalse($v->passes());
+    }
+
     public function testValidateNumeric()
     {
         $trans = $this->getIlluminateArrayTranslator();