diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index be8ea6c994..98202f547b 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -496,7 +496,7 @@ function wpautop( $pee, $br = true ) {
 	$allblocks = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|form|map|area|blockquote|address|math|style|p|h[1-6]|hr|fieldset|legend|section|article|aside|hgroup|header|footer|nav|figure|figcaption|details|menu|summary)';
 
 	// Add a single line break above block-level opening tags.
-	$pee = preg_replace('!(<' . $allblocks . '[^>]*>)!', "\n$1", $pee);
+	$pee = preg_replace('!(<' . $allblocks . '[\s/>])!', "\n$1", $pee);
 
 	// Add a double line break below block-level closing tags.
 	$pee = preg_replace('!(</' . $allblocks . '>)!', "$1\n\n", $pee);
@@ -596,7 +596,9 @@ function wpautop( $pee, $br = true ) {
 		$pee = str_replace(array_keys($pre_tags), array_values($pre_tags), $pee);
 
 	// Restore newlines in all elements.
-	$pee = str_replace( " <!-- wpnl --> ", "\n", $pee );
+	if ( false !== strpos( $pee, '<!-- wpnl -->' ) ) {
+		$pee = str_replace( array( ' <!-- wpnl --> ', '<!-- wpnl -->' ), "\n", $pee );
+	}
 
 	return $pee;
 }
diff --git a/tests/phpunit/tests/formatting/Autop.php b/tests/phpunit/tests/formatting/Autop.php
index e746321061..ccc0d3ac48 100644
--- a/tests/phpunit/tests/formatting/Autop.php
+++ b/tests/phpunit/tests/formatting/Autop.php
@@ -328,6 +328,7 @@ Paragraph two.';
 			'summary',
 		);
 
+		// Check whitespace normalization.
 		$content = array();
 
 		foreach ( $blocks as $block ) {
@@ -335,9 +336,37 @@ Paragraph two.';
 		}
 
 		$expected = join( "\n", $content );
-		$content = join( "\n\n", $content ); // WS difference
+		$input = join( "\n\n", $content ); // WS difference
 
-		$this->assertEquals( $expected, trim( wpautop( $content ) ) );
+		$this->assertEquals( $expected, trim( wpautop( $input ) ) );
+
+		$input = join( "", $content ); // WS difference
+
+		$this->assertEquals( $expected, trim( wpautop( $input ) ) );
+
+		// Check whitespace addition.
+		$content = array();
+
+		foreach ( $blocks as $block ) {
+			$content[] = "<$block/>";
+		}
+
+		$expected = join( "\n", $content );
+		$input = join( "", $content );
+
+		$this->assertEquals( $expected, trim( wpautop( $input ) ) );
+
+		// Check whitespace addition with attributes.
+		$content = array();
+
+		foreach ( $blocks as $block ) {
+			$content[] = "<$block attr='value'>foo</$block>";
+		}
+
+		$expected = join( "\n", $content );
+		$input = join( "", $content );
+
+		$this->assertEquals( $expected, trim( wpautop( $input ) ) );
 	}
 
 	/**
@@ -420,6 +449,14 @@ Paragraph two.';
 				"Hello <!-- a\nhref='world' -->",
 				"<p>Hello <!-- a\nhref='world' --></p>\n",
 			),
+			array(
+				"Hello <!-- <object>\n<param>\n<param>\n<embed>\n</embed>\n</object>\n -->",
+				"<p>Hello <!-- <object>\n<param>\n<param>\n<embed>\n</embed>\n</object>\n --></p>\n",
+			),
+			array(
+				"Hello <!-- <object>\n<param/>\n<param/>\n<embed>\n</embed>\n</object>\n -->",
+				"<p>Hello <!-- <object>\n<param/>\n<param/>\n<embed>\n</embed>\n</object>\n --></p>\n",
+			),
 /* Block elements inside comments will fail this test in all versions, it's not a regression.
 			array(
 				"Hello <!-- <hr> a\nhref='world' -->",