diff --git a/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/GensToVcf.scala b/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/GensToVcf.scala
index 53816acdda3c322d74a8811195bd24d6765f5115..10e5eca751baceeb659e3f602efa0fdc5093b9d0 100644
--- a/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/GensToVcf.scala
+++ b/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/GensToVcf.scala
@@ -52,7 +52,7 @@ class GensToVcf(val root: Configurable) extends ToolCommandFunction with Referen
   override def beforeGraph(): Unit = {
     super.beforeGraph()
     if (reference == null) reference = referenceFasta()
-    if (contig == null) throw new IllegalStateException
+    if (contig == null) throw new IllegalStateException("Contig is missing")
     if (outputVcf.getName.endsWith(".vcf.gz")) outputFiles :+= new File(outputVcf.getAbsolutePath + ".tbi")
   }
 
diff --git a/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/SnptestToVcf.scala b/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/SnptestToVcf.scala
index fd63c3044c5a7acc63c8e32049141ab74af7aa39..e2f938872d070abcd14f889d562efa27da345e4f 100644
--- a/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/SnptestToVcf.scala
+++ b/public/biopet-tools-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/tools/SnptestToVcf.scala
@@ -42,7 +42,7 @@ class SnptestToVcf(val root: Configurable) extends ToolCommandFunction with Refe
   override def beforeGraph(): Unit = {
     super.beforeGraph()
     if (reference == null) reference = referenceFasta()
-    if (contig == null) Logging.addError("SnptestToVcf is missing a contig")
+    if (contig == null) throw new IllegalStateException("Contig is missing")
     //if (outputVcf.getName.endsWith(".vcf.gz")) outputFiles :+= new File(outputVcf.getAbsolutePath + ".tbi")
   }