diff --git a/karate-core/src/main/java/com/intuit/karate/core/ScenarioEngine.java b/karate-core/src/main/java/com/intuit/karate/core/ScenarioEngine.java
index c46941aee..03bb1af64 100644
--- a/karate-core/src/main/java/com/intuit/karate/core/ScenarioEngine.java
+++ b/karate-core/src/main/java/com/intuit/karate/core/ScenarioEngine.java
@@ -1081,7 +1081,7 @@ private Object recurseAndAttach(String name, Object o, Set<Object> seen) {
                 return attachSource(jf.source);
             } catch (Exception e) {
                 logger.warn("[*** attach ***] ignoring js-function: '{}' - {}", name, e.getMessage());
-                return null;
+                return Value.asValue(null); // make sure we return a "dirty" value to force an update
             }
         } else if (o instanceof List) {
             if (seen.add(o)) {