diff --git a/src/hash/crc32/crc32_test.go b/src/hash/crc32/crc32_test.go
index cbb869dfd6..f084612f6f 100644
--- a/src/hash/crc32/crc32_test.go
+++ b/src/hash/crc32/crc32_test.go
@@ -329,11 +329,14 @@ func benchmark(b *testing.B, h hash.Hash32, n, alignment int64) {
 	h.Reset()
 	h.Write(data)
 	h.Sum(in)
+	// Avoid further allocations
+	in = in[:0]
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		h.Reset()
 		h.Write(data)
 		h.Sum(in)
+		in = in[:0]
 	}
 }