diff --git a/daemon/graphdriver/driver.go b/daemon/graphdriver/driver.go
index <HASH>..<HASH> 100644
--- a/daemon/graphdriver/driver.go
+++ b/daemon/graphdriver/driver.go
@@ -11,7 +11,7 @@ import (
 	"github.com/docker/docker/pkg/archive"
 )
 
-type FsMagic uint64
+type FsMagic uint32
 
 const (
 	FsMagicBtrfs = FsMagic(0x9123683E)
FsMagic should avoid sign extension on i<I>

`uint<I>(buf.Type)` on i<I> is ffffffff<I>e on i<I> due to sign extension, so it cannot be compared with `FsMagic(0x<I>E)`