diff --git a/public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/extensions/WigToBigWig.scala b/public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/extensions/WigToBigWig.scala
index c42f2ced1f5776c88131c1b466c7b162d7c875b1..c6ed2e6e49ea70c6e2b3cde5b80092b6fc32e34c 100644
--- a/public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/extensions/WigToBigWig.scala
+++ b/public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/extensions/WigToBigWig.scala
@@ -27,8 +27,8 @@ class WigToBigWig(val root: Configurable) extends BiopetCommandLineFunction {
   var unc: Boolean = config("unc", default = false)
 
   def cmdLine = required(executable) +
-    optional("blockSize=", blockSize, spaceSeparated = false) +
-    optional("itemsPerSlot=", itemsPerSlot, spaceSeparated = false) +
+    optional("-blockSize=", blockSize, spaceSeparated = false) +
+    optional("-itemsPerSlot=", itemsPerSlot, spaceSeparated = false) +
     conditional(clip, "-clip") +
     conditional(unc, "-unc") +
     required(inputWigFile) +