diff --git a/biopet.wdl b/biopet.wdl
index b6fa89310f4b82582d47199a45525636801997e8..91030693ec8b0b074926f020a170482643a5ee6a 100644
--- a/biopet.wdl
+++ b/biopet.wdl
@@ -326,6 +326,8 @@ task ValidateFastq {
         --fastq1 ${fastq1} \
         ${"--fastq2 " + fastq2}
     }
-
+    output {
+        File stderr = stderr()
+    }
 }