diff --git a/webapi/src/main/scala/org/knora/webapi/store/iiif/api/SipiService.scala b/webapi/src/main/scala/org/knora/webapi/store/iiif/api/SipiService.scala
index 79072da61c..f7db7e776a 100644
--- a/webapi/src/main/scala/org/knora/webapi/store/iiif/api/SipiService.scala
+++ b/webapi/src/main/scala/org/knora/webapi/store/iiif/api/SipiService.scala
@@ -5,10 +5,9 @@
 
 package org.knora.webapi.store.iiif.api
 
-import org.apache.pekko.http.scaladsl.marshallers.sprayjson.SprayJsonSupport
-import spray.json.DefaultJsonProtocol
-import spray.json.RootJsonFormat
 import zio.*
+import zio.json.DeriveJsonDecoder
+import zio.json.JsonDecoder
 import zio.macros.accessible
 import zio.nio.file.Path
 
@@ -48,10 +47,15 @@ case class FileMetadataSipiResponse(
   }
 }
 
-object FileMetadataSipiResponse extends SprayJsonSupport with DefaultJsonProtocol {
-  implicit val sipiKnoraJsonResponseFormat: RootJsonFormat[FileMetadataSipiResponse] = jsonFormat8(
-    FileMetadataSipiResponse.apply
-  )
+object FileMetadataSipiResponse {
+  // Because Sipi returns JSON Numbers which are whole numbers but not a valid Scala Int, e.g. `width: 1920.0`, we need to
+  // use a custom decoder for Int. See also https://github.com/zio/zio-json/issues/1049#issuecomment-1814108354
+  implicit val anyWholeNumber: JsonDecoder[Int] = JsonDecoder[Double].mapOrFail { d =>
+    val i = d.toInt
+    if (d == i.toDouble) { Right(i) }
+    else { Left("32-bit int expected") }
+  }
+  implicit val decoder: JsonDecoder[FileMetadataSipiResponse] = DeriveJsonDecoder.gen[FileMetadataSipiResponse]
 }
 
 @accessible
diff --git a/webapi/src/main/scala/org/knora/webapi/store/iiif/impl/SipiServiceLive.scala b/webapi/src/main/scala/org/knora/webapi/store/iiif/impl/SipiServiceLive.scala
index 934788a438..45064376d9 100644
--- a/webapi/src/main/scala/org/knora/webapi/store/iiif/impl/SipiServiceLive.scala
+++ b/webapi/src/main/scala/org/knora/webapi/store/iiif/impl/SipiServiceLive.scala
@@ -5,45 +5,34 @@
 
 package org.knora.webapi.store.iiif.impl
 
-import org.apache.http.Consts
-import org.apache.http.HttpEntity
-import org.apache.http.HttpHost
-import org.apache.http.HttpRequest
-import org.apache.http.HttpResponse
-import org.apache.http.NameValuePair
+import dsp.errors.{BadRequestException, NotFoundException}
+import org.apache.http.{Consts, HttpEntity, HttpHost, HttpRequest, HttpResponse, NameValuePair}
 import org.apache.http.client.config.RequestConfig
 import org.apache.http.client.entity.UrlEncodedFormEntity
 import org.apache.http.client.methods.*
 import org.apache.http.client.protocol.HttpClientContext
 import org.apache.http.config.SocketConfig
-import org.apache.http.impl.client.CloseableHttpClient
-import org.apache.http.impl.client.HttpClients
+import org.apache.http.impl.client.{CloseableHttpClient, HttpClients}
 import org.apache.http.impl.conn.PoolingHttpClientConnectionManager
 import org.apache.http.message.BasicNameValuePair
 import org.apache.http.util.EntityUtils
+import org.knora.webapi.config.{AppConfig, Sipi}
+import org.knora.webapi.messages.admin.responder.usersmessages.UserADM
+import org.knora.webapi.messages.store.sipimessages.*
+import org.knora.webapi.messages.v2.responder.SuccessResponseV2
+import org.knora.webapi.routing.{Jwt, JwtService}
+import org.knora.webapi.slice.admin.domain.service.Asset
+import org.knora.webapi.store.iiif.api.{FileMetadataSipiResponse, SipiService}
+import org.knora.webapi.store.iiif.errors.SipiException
+import org.knora.webapi.util.{SipiUtil, ZScopedJavaIoStreams}
 import spray.json.*
 import zio.*
+import zio.json.DecoderOps
 import zio.nio.file.Path
 
 import java.net.URI
 import java.util
 
-import dsp.errors.BadRequestException
-import dsp.errors.NotFoundException
-import org.knora.webapi.config.AppConfig
-import org.knora.webapi.config.Sipi
-import org.knora.webapi.messages.admin.responder.usersmessages.UserADM
-import org.knora.webapi.messages.store.sipimessages.*
-import org.knora.webapi.messages.v2.responder.SuccessResponseV2
-import org.knora.webapi.routing.Jwt
-import org.knora.webapi.routing.JwtService
-import org.knora.webapi.slice.admin.domain.service.Asset
-import org.knora.webapi.store.iiif.api.FileMetadataSipiResponse
-import org.knora.webapi.store.iiif.api.SipiService
-import org.knora.webapi.store.iiif.errors.SipiException
-import org.knora.webapi.util.SipiUtil
-import org.knora.webapi.util.ZScopedJavaIoStreams
-
 /**
  * Makes requests to Sipi.
  *
@@ -73,7 +62,11 @@ final case class SipiServiceLive(
    */
   override def getFileMetadata(filePath: String): Task[FileMetadataSipiResponse] =
     doSipiRequest(new HttpGet(sipiConfig.internalBaseUrl + filePath + "/knora.json"))
-      .mapAttempt(_.parseJson.convertTo[FileMetadataSipiResponse])
+      .flatMap(bodyStr =>
+        ZIO
+          .fromEither(bodyStr.fromJson[FileMetadataSipiResponse])
+          .mapError(e => SipiException(s"Invalid response from Sipi: $e, $bodyStr"))
+      )
 
   /**
    * Asks Sipi to move a file from temporary storage to permanent storage.