diff --git a/cluster.go b/cluster.go
index f9a4fef..0feebb4 100644
--- a/cluster.go
+++ b/cluster.go
@@ -328,8 +328,6 @@ type ClusterClient struct {
 	closed bool
 }
 
-var _ Cmdable = (*ClusterClient)(nil)
-
 // NewClusterClient returns a Redis Cluster client as described in
 // http://redis.io/topics/cluster-spec.
 func NewClusterClient(opt *ClusterOptions) *ClusterClient {
diff --git a/commands.go b/commands.go
index 0f06652..5132a59 100644
--- a/commands.go
+++ b/commands.go
@@ -236,6 +236,11 @@ type Cmdable interface {
 	Command() *CommandsInfoCmd
 }
 
+var _ Cmdable = (*Client)(nil)
+var _ Cmdable = (*Tx)(nil)
+var _ Cmdable = (*Ring)(nil)
+var _ Cmdable = (*ClusterClient)(nil)
+
 type cmdable struct {
 	process func(cmd Cmder) error
 }
diff --git a/redis.go b/redis.go
index 6fcd5c4..bf46517 100644
--- a/redis.go
+++ b/redis.go
@@ -172,8 +172,6 @@ type Client struct {
 	cmdable
 }
 
-var _ Cmdable = (*Client)(nil)
-
 func newClient(opt *Options, pool pool.Pooler) *Client {
 	base := baseClient{opt: opt, connPool: pool}
 	client := &Client{
diff --git a/ring.go b/ring.go
index 11945b4..96f7294 100644
--- a/ring.go
+++ b/ring.go
@@ -136,8 +136,6 @@ type Ring struct {
 	closed bool
 }
 
-var _ Cmdable = (*Ring)(nil)
-
 func NewRing(opt *RingOptions) *Ring {
 	const nreplicas = 100
 	opt.init()
diff --git a/script.go b/script.go
index c5fc1d2..e569af7 100644
--- a/script.go
+++ b/script.go
@@ -14,6 +14,10 @@ type scripter interface {
 	ScriptLoad(script string) *StringCmd
 }
 
+var _ scripter = (*Client)(nil)
+var _ scripter = (*Ring)(nil)
+var _ scripter = (*ClusterClient)(nil)
+
 type Script struct {
 	src, hash string
 }
diff --git a/tx.go b/tx.go
index 30beda9..c350325 100644
--- a/tx.go
+++ b/tx.go
@@ -23,8 +23,6 @@ type Tx struct {
 	closed bool
 }
 
-var _ Cmdable = (*Tx)(nil)
-
 func (c *Client) newTx() *Tx {
 	tx := Tx{
 		baseClient: baseClient{