diff --git a/src/main/java/org/ligi/passandroid/model/PastLocationsStore.java b/src/main/java/org/ligi/passandroid/model/PastLocationsStore.java
index e8573192..ddbc094a 100644
--- a/src/main/java/org/ligi/passandroid/model/PastLocationsStore.java
+++ b/src/main/java/org/ligi/passandroid/model/PastLocationsStore.java
@@ -30,6 +30,7 @@ public class PastLocationsStore {
         final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         final Set<String> pastLocations = prefs.getStringSet(KEY_PAST_LOCATIONS, new HashSet<String>());
 
+        assert pastLocations != null;
         if (pastLocations.size() >= MAX_ELEMENTS) {
             deleteOneElementFromSet(pastLocations);
         }