diff --git a/src/js/stendhal/util/StringUtil.ts b/src/js/stendhal/util/StringUtil.ts
index 02d4364dd3..e043909f74 100644
--- a/src/js/stendhal/util/StringUtil.ts
+++ b/src/js/stendhal/util/StringUtil.ts
@@ -25,7 +25,10 @@ export namespace StringUtil {
 	 *   `true` if string length excluding whitespace characters is 0.
 	 */
 	export function isEmpty(st: string): boolean {
-		return st.trim().length === 0;
+		if (!st) {
+			return true;
+		}
+		return st.trim() === "";
 	};
 
 	/**