1 files changed, 6 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
index e0c7fa0..0d5a164 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -445,10 +445,16 @@ where
         while !it.is_finished() {
             it = match self.parser.next::<OM, EM>(it.clone(), &mut state) {
                 Some(Ok((rest, output))) => {
+                    debug_assert!(
+                        rest.position() > it.position(),
+                        "iterator failed to make progress"
+                    );
+
                     outputs = OM::combine(outputs, output, |mut acc, e| {
                         acc.push(e);
                         acc
                     });
+
                     rest
                 }
                 _ => break,