diff --git a/source/net/filebot/util/FileUtilities.java b/source/net/filebot/util/FileUtilities.java
index 0e17b042..846cf29b 100644
--- a/source/net/filebot/util/FileUtilities.java
+++ b/source/net/filebot/util/FileUtilities.java
@@ -323,13 +323,13 @@ public final class FileUtilities {
 	}
 
 	public static boolean isDerived(File derivate, File prime) {
-		return isDerived(getName(derivate), prime);
-	}
+		String n = getName(prime).toLowerCase();
+		String s = getName(derivate).toLowerCase();
 
-	public static boolean isDerived(String derivate, File prime) {
-		String base = getName(prime).trim().toLowerCase();
-		derivate = derivate.trim().toLowerCase();
-		return derivate.startsWith(base);
+		if (s.startsWith(n)) {
+			return s.length() == n.length() || !Character.isLetterOrDigit(s.charAt(n.length())); // e.g. x.z is not considered derived from xy.z
+		}
+		return false;
 	}
 
 	public static boolean isDerivedByExtension(File derivate, File prime) {
diff --git a/test/net/filebot/util/FileUtilitiesTest.java b/test/net/filebot/util/FileUtilitiesTest.java
index 8ebf0c14..9fc7185a 100644
--- a/test/net/filebot/util/FileUtilitiesTest.java
+++ b/test/net/filebot/util/FileUtilitiesTest.java
@@ -1,11 +1,11 @@
 
 package net.filebot.util;
 
-
 import static org.junit.Assert.*;
 
-import org.junit.Test;
+import java.io.File;
 
+import org.junit.Test;
 
 public class FileUtilitiesTest {
 
@@ -15,7 +15,6 @@ public class FileUtilitiesTest {
 		assertFalse(FileUtilities.hasExtension(".hidden", "txt"));
 	}
 
-
 	@Test
 	public void getExtension() {
 		assertEquals("txt", FileUtilities.getExtension("abc.txt"));
@@ -28,7 +27,6 @@ public class FileUtilitiesTest {
 		assertEquals(null, FileUtilities.getExtension("archive.invalid extension"));
 	}
 
-
 	@Test
 	public void getNameWithoutExtension() {
 		assertEquals("abc", FileUtilities.getNameWithoutExtension("abc.txt"));
@@ -41,4 +39,13 @@ public class FileUtilitiesTest {
 		assertEquals("archive.invalid extension", FileUtilities.getNameWithoutExtension("archive.invalid extension"));
 	}
 
+	@Test
+	public void isDerived() {
+		assertTrue(FileUtilities.isDerived(new File("avatar.eng.srt"), new File("avatar.mp4")));
+		assertTrue(FileUtilities.isDerived(new File("1.z"), new File("1.xyz")));
+		assertTrue(FileUtilities.isDerived(new File("1.xyz"), new File("1.z")));
+		assertFalse(FileUtilities.isDerived(new File("1.eng.srt"), new File("10.mp4")));
+		assertFalse(FileUtilities.isDerived(new File("10.z"), new File("1.mp4")));
+	}
+
 }