diff --git a/includes/registration/ExtensionProcessor.php b/includes/registration/ExtensionProcessor.php
index 0c19e0907df..4dbb3698a70 100644
--- a/includes/registration/ExtensionProcessor.php
+++ b/includes/registration/ExtensionProcessor.php
@@ -53,8 +53,7 @@ class ExtensionProcessor implements Processor {
 		'ResourceLoaderSources',
 		'RevokePermissions',
 		'SessionProviders',
-		'SpecialPages',
-		'ValidSkinNames',
+		'SpecialPages'
 	];
 
 	/**
@@ -195,6 +194,7 @@ class ExtensionProcessor implements Processor {
 		$this->extractHooks( $info, $path );
 		$this->extractExtensionMessagesFiles( $dir, $info );
 		$this->extractMessagesDirs( $dir, $info );
+		$this->extractSkins( $dir, $info );
 		$this->extractSkinImportPaths( $dir, $info );
 		$this->extractNamespaces( $info );
 		$this->extractResourceLoaderModules( $dir, $info );
@@ -618,6 +618,38 @@ class ExtensionProcessor implements Processor {
 		}
 	}
 
+	/**
+	 * Extract skins and handle path correction for templateDirectory.
+	 *
+	 * @param string $dir
+	 * @param array $info
+	 */
+	protected function extractSkins( $dir, array $info ) {
+		if ( isset( $info['ValidSkinNames'] ) ) {
+			foreach ( $info['ValidSkinNames'] as $skinKey => $data ) {
+				if ( isset( $data['args'][0]['templateDirectory'] ) ) {
+					$templateDirectory = $data['args'][0]['templateDirectory'];
+					$correctedPath = $dir . '/' . $templateDirectory;
+					// Historically the template directory was relative to core
+					// but it really should've been relative to the skin directory.
+					// If the path exists relative to the skin directory, assume that
+					// is what was intended. Otherwise fall back on the previous behavior
+					// of having it relative to core.
+					if ( is_dir( $correctedPath ) ) {
+						$data['args'][0]['templateDirectory'] = $correctedPath;
+					} else {
+						// TODO: deprecate directories relative to core.
+						$data['args'][0]['templateDirectory'] = $templateDirectory;
+					}
+				} elseif ( isset( $data['args'][0] ) ) {
+					// If not set, we set a sensible default.
+					$data['args'][0]['templateDirectory'] = $dir . '/templates';
+				}
+				$this->globals['wgValidSkinNames'][$skinKey] = $data;
+			}
+		}
+	}
+
 	/**
 	 * @param string $dir
 	 * @param array $info
diff --git a/tests/phpunit/includes/registration/ExtensionProcessorTest.php b/tests/phpunit/includes/registration/ExtensionProcessorTest.php
index 1cd8d3bb506..9fe702f2343 100644
--- a/tests/phpunit/includes/registration/ExtensionProcessorTest.php
+++ b/tests/phpunit/includes/registration/ExtensionProcessorTest.php
@@ -62,6 +62,65 @@ class ExtensionProcessorTest extends MediaWikiIntegrationTestCase {
 		);
 	}
 
+	public function testExtractSkins() {
+		$processor = new ExtensionProcessor();
+		$processor->extractInfo( $this->dir, self::$default + [
+			'ValidSkinNames' => [
+				'test-vector' => [
+					'class' => 'SkinTestVector',
+				],
+				'test-vector-empty-args' => [
+					'class' => 'SkinTestVector',
+					'args' => []
+				],
+				'test-vector-empty-options' => [
+					'class' => 'SkinTestVector',
+					'args' => [
+						[]
+					]
+				],
+				'test-vector-core-relative' => [
+					'class' => 'SkinTestVector',
+					'args' => [
+						[
+							'templateDirectory' => 'skins/Vector/templates',
+						]
+					]
+				],
+				'test-vector-skin-relative' => [
+					'class' => 'SkinTestVector',
+					'args' => [
+						[
+							'templateDirectory' => 'templates',
+						]
+					]
+				],
+			]
+		], 1 );
+		$extracted = $processor->getExtractedInfo();
+		$validSkins = $extracted['globals']['wgValidSkinNames'];
+
+		$this->assertArrayHasKey( 'test-vector', $validSkins );
+		$this->assertArrayHasKey( 'test-vector-core-relative', $validSkins );
+		$this->assertArrayHasKey( 'test-vector-empty-args', $validSkins );
+		$this->assertArrayHasKey( 'test-vector-skin-relative', $validSkins );
+		$this->assertSame(
+			$this->dirname . '/templates',
+			$validSkins['test-vector-empty-options']['args'][0]['templateDirectory'],
+			'A sensible default is provided.'
+		);
+		$this->assertSame(
+			'skins/Vector/templates',
+			$validSkins['test-vector-core-relative']['args'][0]['templateDirectory'],
+			'unmodified'
+		);
+		$this->assertSame(
+			$this->dirname . '/templates',
+			$validSkins['test-vector-skin-relative']['args'][0]['templateDirectory'],
+			'modified'
+		);
+	}
+
 	public function testExtractNamespaces() {
 		// Test that namespace IDs defined in extension.json can be overwritten locally
 		if ( !defined( 'MW_EXTENSION_PROCESSOR_TEST_EXTRACT_INFO_X' ) ) {
diff --git a/tests/phpunit/includes/registration/FooBar/templates/README.md b/tests/phpunit/includes/registration/FooBar/templates/README.md
new file mode 100644
index 00000000000..5905bfa195c
--- /dev/null
+++ b/tests/phpunit/includes/registration/FooBar/templates/README.md
@@ -0,0 +1 @@
+This file exists to support ExtensionProcessorTest which checks for directory existence.