diff --git a/biopet-core/src/main/scala/nl/lumc/sasc/biopet/core/MultiSampleQScript.scala b/biopet-core/src/main/scala/nl/lumc/sasc/biopet/core/MultiSampleQScript.scala
index c1cace9c598ed3e5dbf77dad691f60fbcb47aecf..0feeb30704a9ecd1e3964fa1317f15ad49fbc08d 100644
--- a/biopet-core/src/main/scala/nl/lumc/sasc/biopet/core/MultiSampleQScript.scala
+++ b/biopet-core/src/main/scala/nl/lumc/sasc/biopet/core/MultiSampleQScript.scala
@@ -145,7 +145,7 @@ trait MultiSampleQScript extends SummaryQScript { qscript: QScript =>
         ConfigUtils.getMapFromPath(globalConfig.map, List("samples", sampleId, "libraries")).getOrElse(Map()).keySet
       } catch {
         case e: IllegalStateException if e.getMessage == "Value is not a map: library" =>
-          Logging.addError("libraries is not a map")
+          Logging.addError("libraries for samples are not formatted correctly")
           Set()
       }
       if (ids.isEmpty) {