diff --git a/3rdparty b/3rdparty
index 178ffea6b4c68..d8d85fb532f5d 160000
--- a/3rdparty
+++ b/3rdparty
@@ -1 +1 @@
-Subproject commit 178ffea6b4c68f951e31df600f8929ee5466fd62
+Subproject commit d8d85fb532f5de016608f2572a1587f3d9894853
diff --git a/apps/theming/lib/Controller/ThemingController.php b/apps/theming/lib/Controller/ThemingController.php
index 94deb2e73768b..f05edd503701e 100644
--- a/apps/theming/lib/Controller/ThemingController.php
+++ b/apps/theming/lib/Controller/ThemingController.php
@@ -55,7 +55,6 @@
 use OCP\IRequest;
 use OCP\ITempManager;
 use OCP\IURLGenerator;
-use ScssPhp\ScssPhp\Compiler;
 
 /**
  * Class ThemingController
@@ -317,7 +316,7 @@ public function getThemeStylesheet(string $themeId, bool $plain = false, bool $w
 		}
 
 		$theme = $themes[$themeId];
-		$customCss  = $theme->getCustomCss();
+		$customCss  = $theme->getCustomCss("body[data-theme-$themeId]");
 
 		// Generate variables
 		$variables = '';
@@ -330,9 +329,7 @@ public function getThemeStylesheet(string $themeId, bool $plain = false, bool $w
 			$css = ":root { $variables } " . $customCss;
 		} else { 
 			// If not set, we'll rely on the body class
-			$compiler = new Compiler();
-			$compiledCss = $compiler->compileString("body[data-theme-$themeId] { $variables $customCss }");
-			$css = $compiledCss->getCss();;
+			$css = "body[data-theme-$themeId] { $variables } " . $customCss ;
 		}
 
 		try {
diff --git a/apps/theming/lib/ITheme.php b/apps/theming/lib/ITheme.php
index a5c9cdf26a623..82c4d2008bc38 100644
--- a/apps/theming/lib/ITheme.php
+++ b/apps/theming/lib/ITheme.php
@@ -92,8 +92,9 @@ public function getCSSVariables(): array;
 	 * ⚠️ Warning, should be used slightly.
 	 * Theoretically, editing the variables should be enough.
 	 *
+	 * @param string $prefix The css prefix for every rule. It should be appended before every rule.
 	 * @return string
 	 * @since 25.0.0
 	 */
-	public function getCustomCss(): string;
+	public function getCustomCss(string $prefix): string;
 }
diff --git a/apps/theming/lib/Themes/DarkHighContrastTheme.php b/apps/theming/lib/Themes/DarkHighContrastTheme.php
index 62b7d4f6358ba..1f8fb126f2b03 100644
--- a/apps/theming/lib/Themes/DarkHighContrastTheme.php
+++ b/apps/theming/lib/Themes/DarkHighContrastTheme.php
@@ -85,12 +85,12 @@ public function getCSSVariables(): array {
 		return $variables;
 	}
 
-	public function getCustomCss(): string {
+	public function getCustomCss(string $prefix): string {
 		return "
-		[class^='icon-'], [class*=' icon-'],
-			.action,
-			#appmenu li a,
-			.menutoggle {
+			$prefix [class^='icon-'], $prefix [class*=' icon-'],
+			$prefix .action,
+			$prefix #appmenu li a,
+			$prefix .menutoggle {
 				opacity: 1 !important;
 			}
 		";
diff --git a/apps/theming/lib/Themes/DefaultTheme.php b/apps/theming/lib/Themes/DefaultTheme.php
index 58983d29df132..e31cc353470f7 100644
--- a/apps/theming/lib/Themes/DefaultTheme.php
+++ b/apps/theming/lib/Themes/DefaultTheme.php
@@ -209,7 +209,7 @@ public function getCSSVariables(): array {
 		return $variables;
 	}
 
-	public function getCustomCss(): string {
+	public function getCustomCss(string $prefix): string {
 		return '';
 	}
 }
diff --git a/apps/theming/lib/Themes/DyslexiaFont.php b/apps/theming/lib/Themes/DyslexiaFont.php
index 2629ac588c621..093b07005675b 100644
--- a/apps/theming/lib/Themes/DyslexiaFont.php
+++ b/apps/theming/lib/Themes/DyslexiaFont.php
@@ -59,7 +59,7 @@ public function getCSSVariables(): array {
 		return $variables;
 	}
 
-	public function getCustomCss(): string {
+	public function getCustomCss(string $prefix): string {
 		$fontPathWoff = $this->urlGenerator->linkTo('theming', 'fonts/OpenDyslexic-Regular.woff');
 		$fontPathOtf = $this->urlGenerator->linkTo('theming', 'fonts/OpenDyslexic-Regular.otf');
 		$fontPathTtf = $this->urlGenerator->linkTo('theming', 'fonts/OpenDyslexic-Regular.ttf');
diff --git a/apps/theming/lib/Themes/HighContrastTheme.php b/apps/theming/lib/Themes/HighContrastTheme.php
index 77239f2076c24..f55efc3a66510 100644
--- a/apps/theming/lib/Themes/HighContrastTheme.php
+++ b/apps/theming/lib/Themes/HighContrastTheme.php
@@ -78,12 +78,12 @@ public function getCSSVariables(): array {
 		return $variables;
 	}
 
-	public function getCustomCss(): string {
+	public function getCustomCss(string $prefix): string {
 		return "
-			[class^='icon-'], [class*=' icon-'],
-			.action,
-			#appmenu li a,
-			.menutoggle {
+			$prefix [class^='icon-'], $prefix [class*=' icon-'],
+			$prefix .action,
+			$prefix #appmenu li a,
+			$prefix .menutoggle {
 				opacity: 1 !important;
 			}
 		";