diff --git a/includes/EditPage.php b/includes/EditPage.php
index 5b134c118c2..14c58caea3d 100644
--- a/includes/EditPage.php
+++ b/includes/EditPage.php
@@ -2301,7 +2301,7 @@ class EditPage implements IEditObject {
 				if ( $this->sectiontitle !== null ) {
 					// Insert the section title above the content.
 					$content = $content->addSectionHeader( $this->sectiontitle );
-				} elseif ( $this->summary !== '' ) {
+				} else {
 					// Insert the section title above the content.
 					$content = $content->addSectionHeader( $this->summary );
 				}
@@ -4414,7 +4414,7 @@ class EditPage implements IEditObject {
 
 			# If we're adding a comment, we need to show the
 			# summary as the headline
-			if ( $this->section === "new" && $this->summary !== "" ) {
+			if ( $this->section === "new" ) {
 				$content = $content->addSectionHeader( $this->summary );
 			}
 
diff --git a/includes/api/ApiParse.php b/includes/api/ApiParse.php
index 8c2ded9743a..58a4c63dc24 100644
--- a/includes/api/ApiParse.php
+++ b/includes/api/ApiParse.php
@@ -379,7 +379,7 @@ class ApiParse extends ApiBase {
 			if ( $this->section !== false ) {
 				if ( $this->section === 'new' ) {
 					// Insert the section title above the content.
-					if ( $params['sectiontitle'] !== null && $params['sectiontitle'] !== '' ) {
+					if ( $params['sectiontitle'] !== null ) {
 						$this->content = $this->content->addSectionHeader( $params['sectiontitle'] );
 					}
 				} else {
diff --git a/includes/content/WikitextContent.php b/includes/content/WikitextContent.php
index b64f031dbdb..efa4c836cce 100644
--- a/includes/content/WikitextContent.php
+++ b/includes/content/WikitextContent.php
@@ -129,9 +129,8 @@ class WikitextContent extends TextContent {
 	 * @return Content
 	 */
 	public function addSectionHeader( $header ) {
-		$text = wfMessage( 'newsectionheaderdefaultlevel' )
-			->rawParams( $header )->inContentLanguage()->text();
-		$text .= "\n\n";
+		$text = strval( $header ) !== '' ? wfMessage( 'newsectionheaderdefaultlevel' )
+			->plaintextParams( $header )->inContentLanguage()->text() . "\n\n" : '';
 		$text .= $this->getText();
 
 		return new static( $text );
diff --git a/tests/phpunit/includes/api/ApiEditPageTest.php b/tests/phpunit/includes/api/ApiEditPageTest.php
index 13f1b50a321..a7718a505a1 100644
--- a/tests/phpunit/includes/api/ApiEditPageTest.php
+++ b/tests/phpunit/includes/api/ApiEditPageTest.php
@@ -260,10 +260,7 @@ class ApiEditPageTest extends ApiTestCase {
 		$count++;
 		$name = 'Help:ApiEditPageTest_testEditNewSectionSummarySectiontitle' . $count;
 
-		// Create the page first to avoid autogenerated summary for page creation
-		$this->editPage( $name, '' );
-
-		// Test edit
+		// Test edit 1 (new page)
 		$this->doApiRequestWithToken( [
 			'action' => 'edit',
 			'title' => $name,
@@ -276,12 +273,38 @@ class ApiEditPageTest extends ApiTestCase {
 		$wikiPage = WikiPage::factory( Title::newFromText( $name ) );
 
 		// Check the page text is correct
-		$text = $wikiPage->getContent( RevisionRecord::RAW )->getText();
-		$this->assertSame( $expectedText, $text, 'Correct text saved' );
+		$savedText = $wikiPage->getContent( RevisionRecord::RAW )->getText();
+		$this->assertSame( $expectedText, $savedText, 'Correct text saved (new page)' );
 
 		// Check that the edit summary is correct
-		$summary = $wikiPage->getRevisionRecord()->getComment( RevisionRecord::RAW )->text;
-		$this->assertSame( $expectedSummary, $summary, 'Correct summary saved' );
+		// (when not provided or empty, there is an autogenerated summary for page creation)
+		$savedSummary = $wikiPage->getRevisionRecord()->getComment( RevisionRecord::RAW )->text;
+		$expectedSummaryNew = $expectedSummary ?: wfMessage( 'autosumm-new' )->rawParams( $expectedText )
+			->inContentLanguage()->text();
+		$this->assertSame( $expectedSummaryNew, $savedSummary, 'Correct summary saved (new page)' );
+
+		// Clear the page
+		$this->editPage( $name, '' );
+
+		// Test edit 2 (existing page)
+		$this->doApiRequestWithToken( [
+			'action' => 'edit',
+			'title' => $name,
+			'section' => 'new',
+			'text' => 'text',
+			'sectiontitle' => $sectiontitle,
+			'summary' => $summary,
+		] );
+
+		$wikiPage = WikiPage::factory( Title::newFromText( $name ) );
+
+		// Check the page text is correct
+		$savedText = $wikiPage->getContent( RevisionRecord::RAW )->getText();
+		$this->assertSame( $expectedText, $savedText, 'Correct text saved (existing page)' );
+
+		// Check that the edit summary is correct
+		$savedSummary = $wikiPage->getRevisionRecord()->getComment( RevisionRecord::RAW )->text;
+		$this->assertSame( $expectedSummary, $savedSummary, 'Correct summary saved (existing page)' );
 	}
 
 	public function provideEditNewSectionSummarySectiontitle() {
diff --git a/tests/phpunit/includes/content/WikitextContentTest.php b/tests/phpunit/includes/content/WikitextContentTest.php
index 813de688221..fedc823951d 100644
--- a/tests/phpunit/includes/content/WikitextContentTest.php
+++ b/tests/phpunit/includes/content/WikitextContentTest.php
@@ -128,8 +128,11 @@ just a test"
 	public function testAddSectionHeader() {
 		$content = $this->newContent( 'hello world' );
 		$content = $content->addSectionHeader( 'test' );
-
 		$this->assertEquals( "== test ==\n\nhello world", $content->getText() );
+
+		$content = $this->newContent( 'hello world' );
+		$content = $content->addSectionHeader( '' );
+		$this->assertEquals( "hello world", $content->getText() );
 	}
 
 	public static function dataPreSaveTransform() {