diff --git a/MyTracks/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoder.java b/MyTracks/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoder.java
index 0785b5a66..36a4372a5 100644
--- a/MyTracks/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoder.java
+++ b/MyTracks/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoder.java
@@ -32,12 +32,12 @@ public class ChartsExtendedEncoder {
 
   public static String getEncodedValue(int scaled) {
     int index1 = scaled / CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES;
-    int index2 = scaled % CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES;
-
-    if (index1 >= CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES) {
+    if (index1 < 0 || index1 >= CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES) {
       return MISSING_POINT_EXTENDED_ENCODING;
     }
-    if (index2 >= CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES) {
+
+    int index2 = scaled % CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES;
+    if (index2 < 0 || index2 >= CHARTSERVER_EXTENDED_SINGLE_CHARACTER_VALUES) {
       return MISSING_POINT_EXTENDED_ENCODING;
     }
 
diff --git a/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartURLGeneratorTest.java b/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartURLGeneratorTest.java
index 5fba76b2f..d54524d8a 100644
--- a/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartURLGeneratorTest.java
+++ b/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartURLGeneratorTest.java
@@ -1,14 +1,27 @@
-// Copyright 2009 Google Inc. All Rights Reserved.
-
+/*
+ * Copyright 2009 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
 package com.google.android.apps.mytracks.util;
 
 import com.google.android.apps.mytracks.content.Track;
 import com.google.android.apps.mytracks.stats.TripStatistics;
 
-import junit.framework.TestCase;
-
 import java.util.Vector;
 
+import junit.framework.TestCase;
+
 /**
  * Tests for the Chart URL generator.
  *
diff --git a/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoderTest.java b/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoderTest.java
new file mode 100644
index 000000000..96ea5c8b1
--- /dev/null
+++ b/MyTracksTest/src/com/google/android/apps/mytracks/util/ChartsExtendedEncoderTest.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2010 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.android.apps.mytracks.util;
+
+import junit.framework.TestCase;
+
+/**
+ * A unit test for {@link ChartsExtendedEncoder}.
+ * 
+ * @author Bartlomiej Niechwiej
+ */
+public class ChartsExtendedEncoderTest extends TestCase {
+
+  public void testGetEncodedValue_validArguments() {
+    // Valid arguments.
+    assertEquals("AK", ChartsExtendedEncoder.getEncodedValue(10));
+    assertEquals("JO", ChartsExtendedEncoder.getEncodedValue(590));
+    assertEquals("AA", ChartsExtendedEncoder.getEncodedValue(0));
+    // 64^2 = 4096.
+    assertEquals("..", ChartsExtendedEncoder.getEncodedValue(4095));
+  }
+
+  public void testGetEncodedValue_invalidArguments() {
+    // Invalid arguments.
+    assertEquals("__", ChartsExtendedEncoder.getEncodedValue(4096));
+    assertEquals("__", ChartsExtendedEncoder.getEncodedValue(1234564096));
+    assertEquals("__", ChartsExtendedEncoder.getEncodedValue(-10));
+    assertEquals("__", ChartsExtendedEncoder.getEncodedValue(-12324435));
+  }
+
+  public void testGetSeparator() {
+    assertEquals(",", ChartsExtendedEncoder.getSeparator());
+  }
+}