diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/BackupRestoreProgressActivity.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/BackupRestoreProgressActivity.java
index 9d952f1519..cd00708d50 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/BackupRestoreProgressActivity.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/BackupRestoreProgressActivity.java
@@ -92,7 +92,7 @@ public class BackupRestoreProgressActivity extends AbstractGBActivity {
 
         final ZipBackupCallback zipBackupCallback = new ZipBackupCallback() {
             @Override
-            public void onProgress(final int progress, final String message) {
+            public void onProgress(final int progress, final @Nullable String message) {
                 mHandler.post(() -> {
                     backupRestoreProgressBar.setIndeterminate(progress == 0);
                     backupRestoreProgressBar.setProgress(progress);
@@ -102,7 +102,7 @@ public class BackupRestoreProgressActivity extends AbstractGBActivity {
             }
 
             @Override
-            public void onSuccess(final String warnings) {
+            public void onSuccess(final @Nullable String warnings) {
                 mHandler.post(() -> {
                     jobFinished = true;
                     backupRestoreHint.setVisibility(View.GONE);
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/backup/ZipBackupCallback.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/backup/ZipBackupCallback.java
index 0cfbcdae73..40898ee70c 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/backup/ZipBackupCallback.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/backup/ZipBackupCallback.java
@@ -19,9 +19,9 @@ package nodomain.freeyourgadget.gadgetbridge.util.backup;
 import androidx.annotation.Nullable;
 
 public interface ZipBackupCallback {
-    void onProgress(final int progress, final String message);
+    void onProgress(final int progress, @Nullable final String message);
 
-    void onSuccess(final String warnings);
+    void onSuccess(@Nullable final String warnings);
 
     void onFailure(@Nullable final String errorMessage);
 }