diff --git a/biopet/sampleconfig.wdl b/biopet/sampleconfig.wdl
index 3e530ac5c6df802af99564d0af537cb19140ebdc..c8e30e4ba4542f9a040666465ef64cb2aa18938b 100644
--- a/biopet/sampleconfig.wdl
+++ b/biopet/sampleconfig.wdl
@@ -110,7 +110,7 @@ task CaseControl {
 
     output {
         File outputFile = outputPath
-        Array[CaseControl] caseControls = read_json(outputFile)
+        CaseControls caseControls = read_json(outputFile)
     }
 
     runtime {
diff --git a/common.wdl b/common.wdl
index c618cbfdf7d155d6b783f3d8bb8b8dc201fd8d0e..cd434f3971d61c5e26ab585b39342369d0ffdbea 100644
--- a/common.wdl
+++ b/common.wdl
@@ -170,3 +170,7 @@ struct CaseControl {
     String controlName
     IndexedBamFile controlBam
 }
+
+struct CaseControls {
+    Array[CaseControl] caseControls
+}
\ No newline at end of file