diff --git a/zed/src/sum_tree/cursor.rs b/zed/src/sum_tree/cursor.rs
index 5e1624aa877c718c172c520b1c2108db5683a5ce..649b3ad28a8b0f77ba94f4f90d8d47ec13821f0a 100644
--- a/zed/src/sum_tree/cursor.rs
+++ b/zed/src/sum_tree/cursor.rs
@@ -413,7 +413,12 @@ where
         D: Dimension<'a, T::Summary>,
     {
         if let Some(target) = target {
-            debug_assert!(target.cmp(&self.seek_dimension, cx) >= Ordering::Equal);
+            debug_assert!(
+                target.cmp(&self.seek_dimension, cx) >= Ordering::Equal,
+                "cannot seek backward from {:?} to {:?}",
+                self.seek_dimension,
+                target
+            );
         }
 
         if !self.did_seek {