diff --git a/lib/internal/Magento/Framework/View/Page/Config.php b/lib/internal/Magento/Framework/View/Page/Config.php
index 226abc538112b..da7bcb128f4b8 100644
--- a/lib/internal/Magento/Framework/View/Page/Config.php
+++ b/lib/internal/Magento/Framework/View/Page/Config.php
@@ -498,7 +498,7 @@ public function addRss($title, $href)
      */
     public function addBodyClass($className)
     {
-        $className = preg_replace('#[^a-z0-9]+#', '-', strtolower($className));
+        $className = preg_replace('#[^a-z0-9-_]+#', '-', strtolower($className));
         $bodyClasses = $this->getElementAttribute(self::ELEMENT_TYPE_BODY, self::BODY_ATTRIBUTE_CLASS);
         $bodyClasses = $bodyClasses ? explode(' ', $bodyClasses) : [];
         $bodyClasses[] = $className;
diff --git a/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/Generator/BodyTest.php b/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/Generator/BodyTest.php
index 0f59c302f943f..ed926afa00856 100644
--- a/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/Generator/BodyTest.php
+++ b/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/Generator/BodyTest.php
@@ -57,13 +57,13 @@ public function testProcess()
             ->method('getPageConfigStructure')
             ->willReturn($structureMock);
 
-        $bodyClasses = ['class_1', 'class_2'];
+        $bodyClasses = ['class_1', 'class--2'];
         $structureMock->expects($this->once())
             ->method('getBodyClasses')
             ->will($this->returnValue($bodyClasses));
         $this->pageConfigMock->expects($this->exactly(2))
             ->method('addBodyClass')
-            ->withConsecutive(['class_1'], ['class_2']);
+            ->withConsecutive(['class_1'], ['class--2']);
 
         $this->assertEquals(
             $this->bodyGenerator,
diff --git a/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/StructureTest.php b/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/StructureTest.php
index ed15a356cc4c7..d2eba5d2fa1b3 100644
--- a/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/StructureTest.php
+++ b/lib/internal/Magento/Framework/View/Test/Unit/Page/Config/StructureTest.php
@@ -58,7 +58,7 @@ public function testSetElementAttribute()
     public function testSetBodyClass()
     {
         $class1 = 'class_1';
-        $class2 = 'class_2';
+        $class2 = 'class--2';
         $expected = [$class1, $class2];
         $this->structure->setBodyClass($class1);
         $this->structure->setBodyClass($class2);