diff --git a/internal/buffer/buffer.go b/internal/buffer/buffer.go
index 4b25f43756..6c77c2f45b 100644
--- a/internal/buffer/buffer.go
+++ b/internal/buffer/buffer.go
@@ -416,7 +416,10 @@ func NewBuffer(r io.Reader, size int64, path string, startcursor Loc, btype BufT
 		} else if !hasBackup {
 			// since applying a backup does not save the applied backup to disk, we should
 			// not calculate the original hash based on the backup data
-			calcHash(b, &b.origHash)
+			err := calcHash(b, &b.origHash)
+			if err == ErrFileTooLarge {
+				b.Settings["fastdirty"] = true
+			}
 		}
 	}