diff --git a/assets/js/colors.js b/assets/js/colors.js
index 5bc721b51..25f2be076 100644
--- a/assets/js/colors.js
+++ b/assets/js/colors.js
@@ -65,7 +65,9 @@ function updateCssColors() {
 
 // update colors on theme change
 const darkModeMatcher = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)");
-darkModeMatcher?.addEventListener("change", updateCssColors);
+if (darkModeMatcher && darkModeMatcher.addEventListener) {
+  darkModeMatcher.addEventListener("change", updateCssColors);
+}
 // initialize colors
 updateCssColors();
 window.requestAnimationFrame(updateCssColors);
diff --git a/assets/js/theme.js b/assets/js/theme.js
index 130532d2b..a4f42fc83 100644
--- a/assets/js/theme.js
+++ b/assets/js/theme.js
@@ -62,7 +62,9 @@ function updateMetaThemeForBackdrop() {
 }
 
 export function watchThemeChanges() {
-  darkModeMatcher?.addEventListener("change", updateTheme);
+  if (darkModeMatcher && darkModeMatcher.addEventListener) {
+    darkModeMatcher.addEventListener("change", updateTheme);
+  }
   updateTheme();
 
   // listen for modal backdrops