diff --git a/docs/design_docs/segcore/segment_sealed.md b/docs/design_docs/segcore/segment_sealed.md
index 952f6409df..6e06e100af 100644
--- a/docs/design_docs/segcore/segment_sealed.md
+++ b/docs/design_docs/segcore/segment_sealed.md
@@ -1,5 +1,5 @@
 # SegmentSealed
-SegmentSealed has an extra interface rather than segment_inferface:
+SegmentSealed has an extra interface rather than SegmentInterface:
 
 1. `LoadIndex(loadIndexInfo)`: load the index. indexInfo contains
     1. `FieldId`