diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt b/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
index 4187f5008..042ec2777 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
@@ -147,7 +147,7 @@ class SettingsFragment : PreferenceFragmentCompat(), OnSharedPreferenceChangeLis
 
     override fun onSharedPreferenceChanged(
         sharedPreferences: SharedPreferences,
-        key: String
+        key: String?
     ) {
         if (key == "pref_widget_opacity" && widgetUpdater != null) {
             Log.d("SettingsFragment", "updating widgets")
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/preferences/SharedPreferencesStorage.kt b/uhabits-android/src/main/java/org/isoron/uhabits/preferences/SharedPreferencesStorage.kt
index 279357858..febc7f976 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/preferences/SharedPreferencesStorage.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/preferences/SharedPreferencesStorage.kt
@@ -79,7 +79,7 @@ class SharedPreferencesStorage
 
     override fun onSharedPreferenceChanged(
         sharedPreferences: SharedPreferences,
-        key: String
+        key: String?
     ) {
         val preferences = this.preferences ?: return
         sharedPreferences.unregisterOnSharedPreferenceChangeListener(this)