diff --git a/core/src/multi_iterator_scanner.rs b/core/src/multi_iterator_scanner.rs
index b7f96ef63c..866470e8e4 100644
--- a/core/src/multi_iterator_scanner.rs
+++ b/core/src/multi_iterator_scanner.rs
@@ -14,6 +14,7 @@
 //!
 
 /// Output from the element checker used in `MultiIteratorScanner::iterate`.
+#[derive(Debug)]
 pub enum ProcessingDecision {
     /// Should be processed by the scanner.
     Now,