diff --git a/src/main/java/de/dennisguse/opentracks/publicapi/CreateMarkerActivity.java b/src/main/java/de/dennisguse/opentracks/publicapi/CreateMarkerActivity.java
index 501f7630c..5d9eff6cd 100644
--- a/src/main/java/de/dennisguse/opentracks/publicapi/CreateMarkerActivity.java
+++ b/src/main/java/de/dennisguse/opentracks/publicapi/CreateMarkerActivity.java
@@ -23,8 +23,11 @@ public class CreateMarkerActivity extends AppCompatActivity {
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
-        Track.Id trackId = new Track.Id(getIntent().getLongExtra(EXTRA_TRACK_ID, 0L));
+        Track.Id trackId = new Track.Id(getIntent().getLongExtra(EXTRA_TRACK_ID, -1L));
         Location location = getIntent().getParcelableExtra(EXTRA_LOCATION);
+        if (!getIntent().hasExtra(EXTRA_TRACK_ID) || location == null) {
+            throw new IllegalStateException("Parameter 'track_id' and/or 'location' missing or invalid.");
+        }
 
         TrackRecordingServiceConnection.execute(this, (service, self) -> {
             Intent intent = IntentUtils
diff --git a/src/main/java/de/dennisguse/opentracks/publicapi/ShowMarkerActivity.java b/src/main/java/de/dennisguse/opentracks/publicapi/ShowMarkerActivity.java
index 07b47ef3e..9f01a5835 100644
--- a/src/main/java/de/dennisguse/opentracks/publicapi/ShowMarkerActivity.java
+++ b/src/main/java/de/dennisguse/opentracks/publicapi/ShowMarkerActivity.java
@@ -1,30 +1,15 @@
 package de.dennisguse.opentracks.publicapi;
 
 import android.content.Intent;
-import android.database.Cursor;
 import android.os.Bundle;
-import android.util.Log;
-import android.view.View;
 
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
-import androidx.fragment.app.Fragment;
-import androidx.fragment.app.FragmentManager;
-import androidx.fragment.app.FragmentStatePagerAdapter;
-import androidx.viewpager.widget.ViewPager;
 
-import java.util.ArrayList;
 import java.util.List;
 
-import de.dennisguse.opentracks.AbstractActivity;
-import de.dennisguse.opentracks.R;
-import de.dennisguse.opentracks.data.ContentProviderUtils;
 import de.dennisguse.opentracks.data.models.Marker;
 import de.dennisguse.opentracks.databinding.MarkerDetailActivityBinding;
-import de.dennisguse.opentracks.ui.markers.DeleteMarkerDialogFragment.DeleteMarkerCaller;
 import de.dennisguse.opentracks.ui.markers.MarkerDetailActivity;
-import de.dennisguse.opentracks.ui.markers.MarkerDetailFragment;
 import de.dennisguse.opentracks.util.IntentUtils;
 
 /**
@@ -44,10 +29,11 @@ public class ShowMarkerActivity extends AppCompatActivity {
     protected void onCreate(Bundle bundle) {
         super.onCreate(bundle);
 
-        Marker.Id markerId = new Marker.Id(getIntent().getLongExtra(EXTRA_MARKER_ID, 0));
-        if (markerId.id() == 0) {
-            throw new IllegalStateException("No valid markerId provided");
+        if (!getIntent().hasExtra(EXTRA_MARKER_ID)) {
+            throw new IllegalStateException("Parameter 'markerId' missing");
         }
+
+        Marker.Id markerId = new Marker.Id(getIntent().getLongExtra(EXTRA_MARKER_ID, -1));
         Intent intent = IntentUtils.newIntent(this, MarkerDetailActivity.class)
                 .putExtra(MarkerDetailActivity.EXTRA_MARKER_ID, markerId);
         startActivity(intent);