diff --git a/src/main/java/info/textgrid/services/aggregator/html/HTMLWriter.java b/src/main/java/info/textgrid/services/aggregator/html/HTMLWriter.java
index 1389d08b74e171a4d2cb1a0973e5c1acae2b7fc6..f54dd2d0df7f15398beb4fa7b4aa4741db376558 100644
--- a/src/main/java/info/textgrid/services/aggregator/html/HTMLWriter.java
+++ b/src/main/java/info/textgrid/services/aggregator/html/HTMLWriter.java
@@ -205,10 +205,12 @@ public XsltTransformer getTransformer() throws SaxonApiException, IOException {
 		if (getSid().isPresent()) {
 			transformer.setURIResolver(new TGUriResolver(repository, getSid()));
 		}
+		String graphicsURLPattern = repository.getCRUDRestEndpoint()
+				+ "/@URI@/data"
+				+ (getSid().isPresent()? "?sessionId=" + getSid().get() : "");
+		logger.info("Configured graphics URL pattern = " + graphicsURLPattern);
 		transformer.setParameter(new QName("graphicsURLPattern"),
-				new XdmAtomicValue(repository.getCRUDRestEndpoint()
-						+ "/@URI@/data"
-						+ (getSid().isPresent()? "?sessionId=" + getSid().get() : "")));
+				new XdmAtomicValue(graphicsURLPattern));
 		if (css.isPresent()) {
 			transformer.setParameter(new QName("cssFile"), new XdmAtomicValue(
 					css.get()));