diff --git a/app/src/main/java/com/udacity/stockhawk/data/PrefUtils.java b/app/src/main/java/com/udacity/stockhawk/data/PrefUtils.java
index 4e489b52..afab5fa9 100644
--- a/app/src/main/java/com/udacity/stockhawk/data/PrefUtils.java
+++ b/app/src/main/java/com/udacity/stockhawk/data/PrefUtils.java
@@ -39,7 +39,7 @@ public static Set<String> getStocks(Context context) {
 
     private static void editStockPref(Context context, String symbol, Boolean add) {
         String key = context.getString(R.string.pref_stocks_key);
-        Set<String> stocks = getStocks(context);
+        Set<String> stocks = new HashSet<>(getStocks(context));
 
         if (add) {
             stocks.add(symbol);