diff --git a/src/Piwigo.Client/PiwigoContext.cs b/src/Piwigo.Client/PiwigoContext.cs
index c060b57..1c4d3e4 100644
--- a/src/Piwigo.Client/PiwigoContext.cs
+++ b/src/Piwigo.Client/PiwigoContext.cs
@@ -1,4 +1,5 @@
 using System.Net;
+using Flurl;
 using Flurl.Http;
 using Flurl.Http.Content;
 using Microsoft.Extensions.Logging;
@@ -132,7 +133,8 @@ public class PiwigoContext : IPiwigoContext
             throw new ArgumentNullException(nameof(logger));
         }
 
-        return _config.BaseUri.WithCookies(_cookies).ConfigureRequest(r => r.AfterCallAsync = call => LogResponse(call, logger));
+        return _config.BaseUri.AppendPathSegment("ws.php").SetQueryParam("format", "json").WithCookies(_cookies)
+            .ConfigureRequest(r => r.AfterCallAsync = call => LogResponse(call, logger));
     }
 
     private static async Task LogResponse(FlurlCall call, ILogger logger)