diff --git a/dhp-workflows/dhp-doiboost/src/main/java/eu/dnetlib/doiboost/uw/UnpayWallToOAF.scala b/dhp-workflows/dhp-doiboost/src/main/java/eu/dnetlib/doiboost/uw/UnpayWallToOAF.scala
index 0a5ba063f..c8324cde1 100644
--- a/dhp-workflows/dhp-doiboost/src/main/java/eu/dnetlib/doiboost/uw/UnpayWallToOAF.scala
+++ b/dhp-workflows/dhp-doiboost/src/main/java/eu/dnetlib/doiboost/uw/UnpayWallToOAF.scala
@@ -26,7 +26,7 @@ object UnpayWallToOAF {
 
 
   def get_unpaywall_color(input:String):Option[OpenAccessRoute] = {
-    if(input.equalsIgnoreCase("close"))
+    if(input == null || input.equalsIgnoreCase("close"))
       return None
     if(input.equalsIgnoreCase("green"))
       return Some(OpenAccessRoute.green)