diff --git a/src/Readers/Swar4.php b/src/Readers/Swar4.php
index e262294..a1b0173 100644
--- a/src/Readers/Swar4.php
+++ b/src/Readers/Swar4.php
@@ -15,6 +15,7 @@ namespace JeroenED\Libpairtwo\Readers;
 
 use DateTime;
 use JeroenED\Libpairtwo\Enums\TournamentSystem;
+use JeroenED\Libpairtwo\Exceptions\IncompatibleReaderException;
 use JeroenED\Libpairtwo\Interfaces\ReaderInterface;
 use JeroenED\Libpairtwo\Tournament;
 
@@ -33,9 +34,14 @@ class Swar4 implements ReaderInterface
     /** @var string */
     private $release;
 
+    /** @var array  */
+    private const CompatibleVersions = ['v4.'];
+
+
     /**
      * @param string $filename
      * @return ReaderInterface
+     * @throws IncompatibleReaderException
      */
     public function read(string $filename): ReaderInterface
     {
@@ -43,6 +49,10 @@ class Swar4 implements ReaderInterface
 
         $this->setRelease($this->readData('String', $swshandle));
 
+        if (array_search(substr($this->getRelease(), 0, 3), self::CompatibleVersions) === false) {
+            throw new IncompatibleReaderException("This file was not created with Swar 4");
+        }
+
         $this->setTournament(new Tournament());
 
         $this->setBinaryData('Guid', $this->readData('String', $swshandle));