diff --git a/tool/unwrap/unwrap.cwl b/tool/unwrap/unwrap.cwl
index 15219a7..50d900a 100755
--- a/tool/unwrap/unwrap.cwl
+++ b/tool/unwrap/unwrap.cwl
@@ -7,7 +7,7 @@ inputs:
     type: Any?
 expression: |
   ${
-    if (!inputs.input === null) {
+    if (inputs.input === null) {
       throw new Error("Input is null but it should not");
     }
     return {