diff --git a/build.sbt b/build.sbt
index c097195e..0752a932 100644
--- a/build.sbt
+++ b/build.sbt
@@ -78,7 +78,7 @@ pomExtra := <scm>
   </developers>
 
 val luceneV = "8.11.2"
-val sparkVersion = "3.3.3"
+val sparkVersion = "3.5.0"
 
 credentials += Credentials(Path.userHome / ".sbt" / ".credentials")
 
diff --git a/src/test/resources/reference.conf b/src/test/resources/reference.conf
index 17f72bbc..a450b80a 100644
--- a/src/test/resources/reference.conf
+++ b/src/test/resources/reference.conf
@@ -26,7 +26,7 @@ lucenerdd {
     // Lucene index storage
     // Use 'disk' to store the index in Java's temp directory
     // Otherwise the index will be stored in memory
-    store.mode = "memory"
+    store.mode = "disk"
 
     stringfields{