Switchblock grammar Problem

Recently I start use inkle in my Unity Project.
I Write such code in Inky, it works normally.

```
~ temp x=RANDOM(0 ,1)
+[Selection1]
{
-x == 0:
Say hello
-> END
-else:
Say Hi
-> END
}
+[Selection2]
{
-x == 0:
Say hello
-> END
-else:
Say Hi
-> END
}

```
But when I try to check this story in Unity, It throw a fatal error.
Exception: Could not find temporary variable to set: x
I'm confused.