diff --git a/core/Command/Maintenance/Mimetype/UpdateJS.php b/core/Command/Maintenance/Mimetype/UpdateJS.php
index 278e4a2af2cb..61f74d007bd0 100644
--- a/core/Command/Maintenance/Mimetype/UpdateJS.php
+++ b/core/Command/Maintenance/Mimetype/UpdateJS.php
@@ -122,15 +122,17 @@ private function getAppThemes() {
 	private function getLegacyThemes() {
 		$themes = [];
 
-		$legacyThemeDirectories = new \DirectoryIterator(\OC::$SERVERROOT . '/themes/');
+		if (is_dir(\OC::$SERVERROOT . '/themes/')) {
+			$legacyThemeDirectories = new \DirectoryIterator(\OC::$SERVERROOT . '/themes/');
 
-		foreach($legacyThemeDirectories as $legacyThemeDirectory) {
-			if ($legacyThemeDirectory->isFile() || $legacyThemeDirectory->isDot()) {
-				continue;
+			foreach($legacyThemeDirectories as $legacyThemeDirectory) {
+				if ($legacyThemeDirectory->isFile() || $legacyThemeDirectory->isDot()) {
+					continue;
+				}
+				$themes[$legacyThemeDirectory->getFilename()] = $this->getFileTypeIcons(
+					$legacyThemeDirectory->getPathname()
+				);
 			}
-			$themes[$legacyThemeDirectory->getFilename()] = $this->getFileTypeIcons(
-				$legacyThemeDirectory->getPathname()
-			);
 		}
 
 		return $themes;
diff --git a/lib/private/Theme/ThemeService.php b/lib/private/Theme/ThemeService.php
index 09fb5dd31947..3e69db511601 100644
--- a/lib/private/Theme/ThemeService.php
+++ b/lib/private/Theme/ThemeService.php
@@ -166,17 +166,19 @@ private function getAllAppThemes() {
 	 */
 	private function getAllLegacyThemes() {
 		$themes = [];
-		if ($handle = opendir(\OC::$SERVERROOT . '/themes')) {
-			while (false !== ($entry = readdir($handle))) {
-				if ($entry === '.' || $entry === '..') {
-					continue;
-				}
-				if (is_dir(\OC::$SERVERROOT . '/themes/' . $entry)) {
-					$themes[$entry] = $this->makeTheme($entry, false);
+		if (is_dir(\OC::$SERVERROOT . '/themes')) {
+			if ($handle = opendir(\OC::$SERVERROOT . '/themes')) {
+				while (false !== ($entry = readdir($handle))) {
+					if ($entry === '.' || $entry === '..') {
+						continue;
+					}
+					if (is_dir(\OC::$SERVERROOT . '/themes/' . $entry)) {
+						$themes[$entry] = $this->makeTheme($entry, false);
+					}
 				}
+				closedir($handle);
+				return $themes;
 			}
-			closedir($handle);
-			return $themes;
 		}
 		return $themes;
 	}