diff --git a/src/compare/diff.rs b/src/compare/diff.rs
index 1f7e1ce..5d68d32 100644
--- a/src/compare/diff.rs
+++ b/src/compare/diff.rs
@@ -512,7 +512,11 @@ pub fn compare_document<'s>(
                 .ok_or("Should have a corresponding heading.")?;
             child_status.push(compare_heading(rust.source, token, corresponding_heading)?);
         } else {
-            return Err("Document should only contain sections and headlines.".into());
+            return Err(format!(
+                "Document should only contain sections and headlines, found: {}",
+                first_cell
+            )
+            .into());
         }
     }