diff --git a/includes/Title.php b/includes/Title.php
index ef0b02d30c9..9b770039f91 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -1483,13 +1483,18 @@ class Title implements LinkTarget, PageIdentity, IDBAccessObject {
 	 * @since 1.31
 	 */
 	public function getSkinFromConfigSubpage() {
-		$subpage = explode( '/', $this->mTextform );
-		$subpage = $subpage[count( $subpage ) - 1];
-		$lastdot = strrpos( $subpage, '.' );
-		if ( $lastdot === false ) {
-			return $subpage; # Never happens: only called for names ending in '.css'/'.json'/'.js'
+		$text = $this->getText();
+		$lastSlashPos = $this->findSubpageDivider( $text, -1 );
+		if ( $lastSlashPos === false ) {
+			return '';
 		}
-		return substr( $subpage, 0, $lastdot );
+
+		$lastDot = strrpos( $text, '.', $lastSlashPos );
+		if ( $lastDot === false ) {
+			return '';
+		}
+
+		return substr( $text, $lastSlashPos + 1, $lastDot - $lastSlashPos - 1 );
 	}
 
 	/**
diff --git a/tests/phpunit/includes/TitleMethodsTest.php b/tests/phpunit/includes/TitleMethodsTest.php
index c67a31dad31..c425b9b55b0 100644
--- a/tests/phpunit/includes/TitleMethodsTest.php
+++ b/tests/phpunit/includes/TitleMethodsTest.php
@@ -193,6 +193,30 @@ class TitleMethodsTest extends MediaWikiLangTestCase {
 		);
 	}
 
+	public function provideGetSkinFromConfigSubpage() {
+		return [
+			[ 'User:Foo', '' ],
+			[ 'User:Foo.css', '' ],
+			[ 'User:Foo/', '' ],
+			[ 'User:Foo/bar', '' ],
+			[ 'User:Foo./bar', '' ],
+			[ 'User:Foo/bar.', 'bar' ],
+			[ 'User:Foo/bar.css', 'bar' ],
+			[ '/bar.css', '' ],
+			[ '//bar.css', 'bar' ],
+			[ '.css', '' ],
+		];
+	}
+
+	/**
+	 * @dataProvider provideGetSkinFromConfigSubpage
+	 * @covers Title::getSkinFromConfigSubpage
+	 */
+	public function testGetSkinFromConfigSubpage( $title, $expected ) {
+		$title = Title::newFromText( $title );
+		$this->assertSame( $expected, $title->getSkinFromConfigSubpage() );
+	}
+
 	public static function provideIsUserConfigPage() {
 		return [
 			[ 'Help:Foo', false ],