Stored procerdure returns null as output parameter

Stored procerdure returns null as output parameter

I have stored procedure, which works great in MS SQL management studio.
When I try to use it in VS rows returns fine, but value of output
parameters is NULL.
SqlCommand cmd = new SqlCommand("proc_name", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new SqlParameter("@p_SomeVal", SqlDbType.Int));
cmd.Parameters["@p_SomeVal"].Direction = ParameterDirection.Output;
rdr = cmd.ExecuteReader();
//...process rows...
if (cmd.Parameters["@p_SomeVal"].Value != null)
SomeVal = (int)cmd.Parameters["@p_SomeVal"].Value;