diff --git a/src/main/java/it/gov/pagopa/fdr/service/history/HistoryService.java b/src/main/java/it/gov/pagopa/fdr/service/history/HistoryService.java
index e28e020f..941086a3 100644
--- a/src/main/java/it/gov/pagopa/fdr/service/history/HistoryService.java
+++ b/src/main/java/it/gov/pagopa/fdr/service/history/HistoryService.java
@@ -123,8 +123,8 @@ public HistoryBlobBody saveJsonFile(
         objMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
         String fdrHistoryEntityJson = objMapper.writeValueAsString(fdrHistoryEntity);
         isJsonValid(fdrHistoryEntityJson, jsonSchema);
-        String compressedFdrHistoryEntityJson = StringUtil.zip(fdrHistoryEntityJson);
-        BinaryData jsonFile = BinaryData.fromString(compressedFdrHistoryEntityJson);
+        byte[] compressedFdrHistoryEntityJson = StringUtil.zip(fdrHistoryEntityJson);
+        BinaryData jsonFile = BinaryData.fromBytes(compressedFdrHistoryEntityJson);
 
         uploadBlob(fileName, jsonFile);
         return HistoryBlobBody.builder()
diff --git a/src/main/java/it/gov/pagopa/fdr/service/re/ReService.java b/src/main/java/it/gov/pagopa/fdr/service/re/ReService.java
index c7c7c75b..f9c688b2 100644
--- a/src/main/java/it/gov/pagopa/fdr/service/re/ReService.java
+++ b/src/main/java/it/gov/pagopa/fdr/service/re/ReService.java
@@ -21,7 +21,6 @@
 import jakarta.enterprise.context.ApplicationScoped;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.util.Arrays;
@@ -115,16 +114,14 @@ public <T extends ReAbstract> void writeBlobIfExist(T re) {
                 "%s_%s_%s.json.zip",
                 re.getSessionId(), re.getFdrAction(), reInterface.getHttpType().name());
 
-        String compressedBody = null;
+        byte[] compressedBody = null;
         try {
           compressedBody = StringUtil.zip(bodyStr);
         } catch (IOException e) {
           log.errorf("Compress json error", e);
           throw new AppException(AppErrorCodeMessageEnum.COMPRESS_JSON);
         }
-        BinaryData body =
-            BinaryData.fromStream(
-                new ByteArrayInputStream(compressedBody.getBytes(StandardCharsets.UTF_8)));
+        BinaryData body = BinaryData.fromStream(new ByteArrayInputStream(compressedBody));
         BlobClient blobClient = blobContainerClient.getBlobClient(fileName);
         blobClient.upload(body);
 
diff --git a/src/main/java/it/gov/pagopa/fdr/util/StringUtil.java b/src/main/java/it/gov/pagopa/fdr/util/StringUtil.java
index 2c521e41..519e64c0 100644
--- a/src/main/java/it/gov/pagopa/fdr/util/StringUtil.java
+++ b/src/main/java/it/gov/pagopa/fdr/util/StringUtil.java
@@ -7,13 +7,13 @@
 
 public class StringUtil {
 
-  public static String zip(String str) throws IOException {
+  public static byte[] zip(String str) throws IOException {
     byte[] strBytes = str.getBytes(StandardCharsets.UTF_8);
     ByteArrayOutputStream bais = new ByteArrayOutputStream(strBytes.length);
     GZIPOutputStream gzipOut = new GZIPOutputStream(bais);
     gzipOut.write(strBytes);
     gzipOut.close();
-    String compressed = bais.toString(StandardCharsets.UTF_8);
+    byte[] compressed = bais.toByteArray();
     bais.close();
     return compressed;
   }