diff --git a/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportData.java b/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportData.java
index e241271bba7b6ef3c375866639eda13f7d369ab7..bea5d003d18ce25769862c1f57f22e92584e469e 100644
--- a/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportData.java
+++ b/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportData.java
@@ -1,6 +1,6 @@
 package de.ozgcloud.alfa.export;
 
-import java.util.List;
+import java.util.Set;
 
 import de.ozgcloud.alfa.common.file.OzgFile;
 import de.xoev.xdomea.AbgabeAbgabe0401;
@@ -16,6 +16,6 @@ class ExportData {
 
 	private String exportFilename;
 	private AbgabeAbgabe0401 abgabe;
-	private List<OzgFile> exportFiles;
+	private Set<OzgFile> exportFiles;
 
 }
diff --git a/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportService.java b/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportService.java
index dfa730ff9003f54fcef6bc626d36c471dccec27e..65de7b375a079150afa974bd1dfc23ea0607b598 100644
--- a/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportService.java
+++ b/alfa-xdomea/src/main/java/de/ozgcloud/alfa/export/ExportService.java
@@ -6,8 +6,9 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.charset.StandardCharsets;
-import java.util.List;
 import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
@@ -78,7 +79,7 @@ class ExportService {
 						postfachMailData.getAttachments().stream(),
 						bescheidData.getFiles().stream())
 				.flatMap(s -> s)
-				.toList();
+				.collect(Collectors.toSet());
 		return ExportData.builder().abgabe(abgabe).exportFilename(buildXmlFilename(filenameId)).exportFiles(exportFiles).build();
 	}
 
@@ -114,7 +115,7 @@ class ExportService {
 		zipOutputStream.closeEntry();
 	}
 
-	private void putFilesIntoZip(List<OzgFile> ozgFiles, ZipOutputStream zipOutputStream) {
+	private void putFilesIntoZip(Set<OzgFile> ozgFiles, ZipOutputStream zipOutputStream) {
 		ozgFiles.forEach(ozgFile -> putOzgFileIntoZip(ozgFile, zipOutputStream));
 	}
 
diff --git a/alfa-xdomea/src/test/java/de/ozgcloud/alfa/export/ExportDataTestFactory.java b/alfa-xdomea/src/test/java/de/ozgcloud/alfa/export/ExportDataTestFactory.java
index b6b8549770ace6c03514451fc6a5ab115af2b50f..84f4c718b85e1b76c6fa69fa3103fbd0c62fbe51 100644
--- a/alfa-xdomea/src/test/java/de/ozgcloud/alfa/export/ExportDataTestFactory.java
+++ b/alfa-xdomea/src/test/java/de/ozgcloud/alfa/export/ExportDataTestFactory.java
@@ -1,6 +1,6 @@
 package de.ozgcloud.alfa.export;
 
-import java.util.List;
+import java.util.Set;
 
 import de.ozgcloud.alfa.common.file.OzgFile;
 import de.ozgcloud.alfa.common.file.OzgFileTestFactory;
@@ -20,6 +20,6 @@ class ExportDataTestFactory {
 		return ExportData.builder()
 				.exportFilename(EXPORT_FILENAME)
 				.abgabe(ABGABE)
-				.exportFiles(List.of(OZG_FILE));
+				.exportFiles(Set.of(OZG_FILE));
 	}
 }