Template default parameters question

[DMisener]

I am obviously missing something here regarding optional defaulted parameters 
using templates:
    
    
    # Defaulting is supported in the following (even when there is an untyped 
parameter)
    var lastGreeting: string
    
    template greet*(lastGreeting: untyped, text = "Hello", who = "Bob") =
      lastGreeting = text & " " & who
      echo lastGreeting
    
    greet lastGreeting
    greet(lastGreeting, "Hi")
    greet(lastGreeting, "Salute", "Fred")
    greet(lastGreeting, who = "Tom")
    
    echo "\nLastGreeting: ", lastGreeting
    
    # Generates the expected output:
    # Hello Bob
    # Hi Bob
    # Salute Fred
    # Hello Tom
    #
    # LastGreeting: Hello Tom
    
    echo "---"
    
    # Now for my *failing* example template with optional parameters
    
    let Chrome = "Chrome"
    
    template webSession*(
      sessionInfo: untyped,
      baseURL: string,
      browser = Chrome,
      headless = true,
      actions: untyped
      ) =
      
      # Mock open session
      var sessionInfo =
        "open Session(" &
        "baseURL=" & "\"" & baseURL & "\", " &
        "browser=" & $browser & ", " &
        "headless=" & $headless & ")"
      
      actions
      
      # Mock session cleanup
      echo "close Session"
    
    # The following works fine and outputs:
    #   open Session(baseURL="https://mysite.com";, browser=Chrome, 
headless=false)
    #   close Session
    
    webSession(mySite, "https://mysite.com";, Chrome, false):
      echo mySite
    
    # But actually trying to use default parameters:
    
    # webSession(mySite, "https://mysite.com";):
    #   echo mySite
    
    # Fails to compile with the following error:
    #
    # Expression: webSession(mySite, "https://mysite.com";) do:
    #   echo [mySite]
    #   [1] mySite: string
    #   [2] "https://mysite.com": string
    #   [3]
    # echo [mySite]: void
    #
    # Expected one of (first mismatch at [position]):
    # [3] template webSession(sessionInfo: untyped; baseURL: string; browser = 
Chrome;
    #                     headless = true; actions: untyped): untyped
    
    
    
    Run

I can't see what is different from the top example and the failing one. What 
silly thing am I missing :-)