storage/wrappers.go | 15 +++++++++------

diff --git a/storage/wrappers.go b/storage/wrappers.go
index 044a1f5aa53fd62de03e4cdeed76e14d1f4189f6..4fc0e10d6208445ac2be8332964e9ee57381ca1b 100644
--- a/storage/wrappers.go
+++ b/storage/wrappers.go
@@ -1,7 +1,6 @@
 package storage
 
 import (
-	"errors"
 	"io"
 	"os"
 
@@ -37,11 +36,15 @@ 	mip metainfo.Piece
 }
 
 func (p Piece) WriteAt(b []byte, off int64) (n int, err error) {
-	c := p.Completion()
-	if c.Ok && c.Complete {
-		err = errors.New("piece already completed")
-		return
-	}
+	// Callers should not be writing to completed pieces, but it's too
+	// expensive to be checking this on every single write using uncached
+	// completions.
+
+	// c := p.Completion()
+	// if c.Ok && c.Complete {
+	// 	err = errors.New("piece already completed")
+	// 	return
+	// }
 	if off+int64(len(b)) > p.mip.Length() {
 		panic("write overflows piece")
 	}