diff --git a/quickwit/quickwit-storage/src/object_storage/s3_compatible_storage.rs b/quickwit/quickwit-storage/src/object_storage/s3_compatible_storage.rs
index 19652005e1b..7ebd1fdb32e 100644
--- a/quickwit/quickwit-storage/src/object_storage/s3_compatible_storage.rs
+++ b/quickwit/quickwit-storage/src/object_storage/s3_compatible_storage.rs
@@ -323,6 +323,15 @@ impl S3CompatibleObjectStorage {
         payload: Box<dyn crate::PutPayload>,
         len: u64,
     ) -> Result<(), Retry<StorageError>> {
+        // For MD5 uploads, compute Content-MD5 before streaming the body.
+        // The AWS SDK no-ops ChecksumAlgorithm::Md5, so MD5 must be sent via
+        // the legacy Content-MD5 header (same as the multipart path does per part).
+        let content_md5: Option<String> = self
+            .maybe_compute_part_md5(payload.as_ref(), 0..len)
+            .await
+            .map_err(|err| Retry::Permanent(StorageError::from(err)))?
+            .map(|digest| BASE64_STANDARD.encode(digest.0));
+
         let body = payload
             .byte_stream()
             .await
@@ -338,6 +347,7 @@ impl S3CompatibleObjectStorage {
             .body(body)
             .content_length(len as i64)
             .set_checksum_algorithm(aws_checksum_algorithm(self.checksum_algorithm))
+            .set_content_md5(content_md5)
             .send()
             .await
             .map_err(|sdk_error| {
@@ -1305,4 +1315,77 @@ mod tests {
             .await
             .unwrap();
     }
+
+    fn make_s3_storage_with_replay(
+        client: StaticReplayClient,
+        checksum_algorithm: quickwit_config::ChecksumAlgorithm,
+    ) -> S3CompatibleObjectStorage {
+        let credentials = Credentials::new("mock_key", "mock_secret", None, None, "mock_provider");
+        let config = aws_sdk_s3::Config::builder()
+            .behavior_version(aws_behavior_version())
+            .region(Some(Region::new("us-east-1")))
+            .http_client(client)
+            .credentials_provider(credentials)
+            .build();
+        S3CompatibleObjectStorage {
+            s3_client: S3Client::from_conf(config),
+            uri: Uri::for_test("s3://bucket/"),
+            bucket: "bucket".to_string(),
+            prefix: PathBuf::new(),
+            multipart_policy: MultiPartPolicy::default(),
+            retry_params: RetryParams::for_test(),
+            disable_multi_object_delete: false,
+            disable_multipart_upload: true,
+            checksum_algorithm,
+        }
+    }
+
+    fn ok_put_response() -> ReplayEvent {
+        ReplayEvent::new(
+            http::Request::builder().body(SdkBody::empty()).unwrap(),
+            http::Response::builder()
+                .status(200)
+                .body(SdkBody::empty())
+                .unwrap(),
+        )
+    }
+
+    #[tokio::test]
+    async fn test_single_part_upload_sets_content_md5_for_md5_algorithm() {
+        let client = StaticReplayClient::new(vec![ok_put_response()]);
+        let s3_storage =
+            make_s3_storage_with_replay(client.clone(), quickwit_config::ChecksumAlgorithm::Md5);
+        let payload: Vec<u8> = b"hello world".to_vec();
+        s3_storage
+            .put(Path::new("test-key"), Box::new(payload.clone()))
+            .await
+            .unwrap();
+
+        let requests = client.actual_requests().collect::<Vec<_>>();
+        assert_eq!(requests.len(), 1);
+        let content_md5 = requests[0]
+            .headers()
+            .get("content-md5")
+            .expect("Content-MD5 header must be present for md5 checksum algorithm");
+        let expected = BASE64_STANDARD.encode(md5::compute(&payload).0);
+        assert_eq!(content_md5, expected.as_str());
+    }
+
+    #[tokio::test]
+    async fn test_single_part_upload_no_content_md5_for_crc32c_algorithm() {
+        let client = StaticReplayClient::new(vec![ok_put_response()]);
+        let s3_storage =
+            make_s3_storage_with_replay(client.clone(), quickwit_config::ChecksumAlgorithm::Crc32c);
+        s3_storage
+            .put(Path::new("test-key"), Box::new(b"hello world".to_vec()))
+            .await
+            .unwrap();
+
+        let requests = client.actual_requests().collect::<Vec<_>>();
+        assert_eq!(requests.len(), 1);
+        assert!(
+            requests[0].headers().get("content-md5").is_none(),
+            "Content-MD5 header must not be set for crc32c checksum algorithm"
+        );
+    }
 }