diff --git a/src/operation_transformation/edited_text.rs b/src/operation_transformation/edited_text.rs
index 60f32da..c287903 100644
--- a/src/operation_transformation/edited_text.rs
+++ b/src/operation_transformation/edited_text.rs
@@ -144,21 +144,21 @@ where
                 Operation::Insert { .. } | Operation::Equal { .. }
             );
 
-            let original_length = operation.len() as i64;
+            let original_length = operation.len() as isize;
             let result = match side {
                 Side::Left => {
                     let result = operation.merge_operations(&mut last_other_op);
 
                     if let ref op @ (Operation::Insert { .. } | Operation::Equal { .. }) = result {
-                        let shift = merged_length as i64 - seen_left_length as i64
-                            + op.len() as i64
+                        let shift = merged_length as isize - seen_left_length as isize
+                            + op.len() as isize
                             - original_length;
 
                         while let Some(cursor) = left_cursors.next_if(|cursor| {
                             cursor.char_index <= seen_left_length + original_length as usize
                         }) {
                             merged_cursors.push(
-                                cursor.with_index((cursor.char_index as i64 + shift) as usize),
+                                cursor.with_index(cursor.char_index.saturating_add_signed(shift)),
                             );
                         }
                     }
@@ -176,15 +176,15 @@ where
                     let result = operation.merge_operations(&mut last_other_op);
 
                     if let ref op @ (Operation::Insert { .. } | Operation::Equal { .. }) = result {
-                        let shift = merged_length as i64 - seen_right_length as i64
-                            + op.len() as i64
+                        let shift = merged_length as isize - seen_right_length as isize
+                            + op.len() as isize
                             - original_length;
 
                         while let Some(cursor) = right_cursors.next_if(|cursor| {
                             cursor.char_index <= seen_right_length + original_length as usize
                         }) {
                             merged_cursors.push(
-                                cursor.with_index((cursor.char_index as i64 + shift) as usize),
+                                cursor.with_index(cursor.char_index.saturating_add_signed(shift)),
                             );
                         }
                     }
diff --git a/src/types/text_with_cursors.rs b/src/types/text_with_cursors.rs
index ac7c18f..c9dec89 100644
--- a/src/types/text_with_cursors.rs
+++ b/src/types/text_with_cursors.rs
@@ -20,7 +20,9 @@ impl TextWithCursors {
             debug_assert!(
                 cursor.char_index <= length,
                 // cursor.char_index == length means that the cursor is at the end
-                "Cursor positions must be contained within the text or just after the end"
+                "Cursor positions ({}) must be contained within the text (of length {length}) or \
+                 just after the end",
+                cursor.char_index
             );
         }
 
diff --git a/tests/examples/various.yml b/tests/examples/various.yml
index 4576edc..4370178 100644
--- a/tests/examples/various.yml
+++ b/tests/examples/various.yml
@@ -9,6 +9,12 @@ left: Party C shall pay Party B
 right: Party A shall receive from Party B
 expected: Party C shall receive from Party B
 
+---
+parent: hello
+left: hel|lo
+right: hi
+expected: "|hi"
+
 ---
 parent:
 left: hi my friend|