diff --git a/cli/encode-server/encode.go b/cli/encode-server/encode.go
index c2d9218..83b1ea1 100644
--- a/cli/encode-server/encode.go
+++ b/cli/encode-server/encode.go
@@ -87,7 +87,7 @@ func encodeFromReader(reader io.ReadCloser, job *Job, inputMimeType string, w ht
 		decProps.FullColorRange != job.Config.Properties.FullColorRange ||
 		decProps.TimeBase() != job.Config.Properties.TimeBase() {
 		w.Header().Set("x-encoder-error", "")
-		w.Header().Set("x-decoder-error", "mismatched config properties")
+		w.Header().Set("x-decoder-error", fmt.Sprintf("mismatched config properties: job %v != decoded %v", job.Config.Properties, decProps))
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}