diff --git a/rx-preferences/src/main/java/com/f2prateek/rx/preferences2/StringSetAdapter.java b/rx-preferences/src/main/java/com/f2prateek/rx/preferences2/StringSetAdapter.java
index ae0270c..62827f4 100644
--- a/rx-preferences/src/main/java/com/f2prateek/rx/preferences2/StringSetAdapter.java
+++ b/rx-preferences/src/main/java/com/f2prateek/rx/preferences2/StringSetAdapter.java
@@ -13,7 +13,11 @@ final class StringSetAdapter implements Preference.Adapter<Set<String>> {
   static final StringSetAdapter INSTANCE = new StringSetAdapter();
 
   @Override public Set<String> get(@NonNull String key, @NonNull SharedPreferences preferences) {
-    return Collections.unmodifiableSet(preferences.getStringSet(key, null));
+    Set<String> set = preferences.getStringSet(key, null);
+    if (set == null) {
+      return null;
+    }
+    return Collections.unmodifiableSet(set);
   }
 
   @Override public void set(@NonNull String key, @NonNull Set<String> value,