diff --git a/daemon/graphdriver/devmapper/README.md b/daemon/graphdriver/devmapper/README.md
index 181b58003f..bf6f2c792c 100644
--- a/daemon/graphdriver/devmapper/README.md
+++ b/daemon/graphdriver/devmapper/README.md
@@ -129,11 +129,11 @@ Here is the list of supported options:
  *  `dm.blocksize`
 
     Specifies a custom blocksize to use for the thin pool.  The default
-    blocksize is 512K.
+    blocksize is 64K.
 
     Example use:
 
-    ``docker -d --storage-opt dm.blocksize=64K``
+    ``docker -d --storage-opt dm.blocksize=512K``
 
  *  `dm.blkdiscard`
 
diff --git a/daemon/graphdriver/devmapper/deviceset.go b/daemon/graphdriver/devmapper/deviceset.go
index 61ba81852d..3c36a22cb8 100644
--- a/daemon/graphdriver/devmapper/deviceset.go
+++ b/daemon/graphdriver/devmapper/deviceset.go
@@ -28,7 +28,7 @@ var (
 	DefaultDataLoopbackSize     int64  = 100 * 1024 * 1024 * 1024
 	DefaultMetaDataLoopbackSize int64  = 2 * 1024 * 1024 * 1024
 	DefaultBaseFsSize           uint64 = 10 * 1024 * 1024 * 1024
-	DefaultThinpBlockSize       uint32 = 1024 // 512K = 1024 512b sectors
+	DefaultThinpBlockSize       uint32 = 128 // 64K = 128 512b sectors
 )
 
 type DevInfo struct {