Duplicate keys in PK, in Read Committed Snapshot Isolation Level

Question

Read Committed Snapshot Isolation Level,

Create Table Tmp(ID Int Primary Key);

In one session (query in the SSMS):

Begin Tran
Insert Into Tmp(ID) Select 1 Where Not Exists (Select * From Tmp Where ID=1);

The code runs successfully and waits for either Commit or RollBack. In another session the same code:

Begin Tran
Insert Into Tmp(ID) Select 1 Where Not Exists (Select * From Tmp Where ID=1);

The code runs and remains locked, waiting for the first session to release the table.

In the first session I run

Commit

It finishes successfully, but the second session fails despite the "Where Not Exists" predicate:

Violation of Primary Key Constraint ..

How can I avoid it and finish the second one successfully (without inserting any row), or to avoid in advance the second transaction?