diff --git a/lightwallet/commands.go b/lightwallet/commands.go
index 88dcb97..a2c8392 100644
--- a/lightwallet/commands.go
+++ b/lightwallet/commands.go
@@ -7,6 +7,8 @@ import (
 
 const (
 	InsInit = uint8(0xFE)
+
+	tagSelectResponsePreInitialized = uint8(0x80)
 )
 
 func NewCommandInit(data []byte) *apdu.Command {
diff --git a/lightwallet/installer.go b/lightwallet/installer.go
index 857d376..173c4bb 100644
--- a/lightwallet/installer.go
+++ b/lightwallet/installer.go
@@ -74,6 +74,11 @@ func (i *Installer) Init() (*Secrets, error) {
 		return nil, err
 	}
 
+	if resp.Data[0] != tagSelectResponsePreInitialized {
+		err := fmt.Errorf("card already initialized (%x).", resp.Data[0])
+		return nil, err
+	}
+
 	cardKeyData := resp.Data[2:]
 	secureChannel, err := NewSecureChannel(i.c, cardKeyData)
 	if err != nil {
@@ -91,8 +96,6 @@ func (i *Installer) Init() (*Secrets, error) {
 		return nil, err
 	}
 
-	fmt.Printf("RESP: %+v\n", resp)
-
 	return secrets, nil
 }