diff --git a/docs/design_docs/segcore/segment_sealed.md b/docs/design_docs/segcore/segment_sealed.md
index 72945c8144..1942011e9e 100644
--- a/docs/design_docs/segcore/segment_sealed.md
+++ b/docs/design_docs/segcore/segment_sealed.md
@@ -38,4 +38,4 @@ Search is executable as long as all the columns involved in the search are loade
 # SegmentSealedImpl internal function definition
 1. Most functions are the implementation of the corresponding functions of segment interface, which will not be repeated here
 2. `update_row_count`: Used to update the row_count field
-3. `mask_with_timestamps`: Use Timestamp column to update search bitmask，used to support Time Travel function
+3. `mask_with_timestamps`: Use Timestamp column to update search bitmask, used to support Time Travel function