Whitespacing parsing changes between 1.3.1 and 1.6.4?

I'm finally upgrading a project which was using velocity 1.3.1 to
1.6.4 (I might go with something newer, but I wanted to try to keep
things as simple as possible for a first try without adding the 1.7
new features, and Cayenne is using 1.6.4 right now).

One thing that hit me right away was that tabs are no longer allowed
between a directive and the left paren:

#set<tab>( $amountString = "Pay In Full" )

now dies with the following, and the error context is misleading.

ERROR [main 04-01 09:45:42] velocity:
org.apache.velocity.runtime.parser.ParseException: Encountered "=" at
line 190, column 25.
Was expecting one of:
    <RPAREN> ...
    "," ...
    <IDENTIFIER> ...
    "{" ...
    <WORD> ...
    <STRING_LITERAL> ...
    <INTEGER_LITERAL> ...
    "[" ...
    <FLOATING_POINT_LITERAL> ...
    "{" ...
    "true" ...
    "false" ...

The same thing happens with #if<tab>.  Replacing the tabs with spaces
causes the error to go away.

Is this a known issue with 1.6.4, or something that is a regression
for all recent versions of velocity?

I've been using whitespace between the directive and the left-paren to
provide indentation to make templates more readable, so this affects a
lot of code.    Replacing it with spaces could eventually happen, but
I don't have something automatic at hand to do it.

Thanks!