[exim] Integer expected for max_rcpt

Hello,

I want to use an expansion to set the value for max_rcpt in transport.
So I try the following:

max_rcpt = ${if def:acl_m_singlesend {1}{100}}

or

max_rcpt = ${eval10:${if def:acl_m_singlesend {1}{100}}}

But in both trys I get the message »integer expected for max_rcpt«.

I use exim 4.71. Is there any way to convert a string into a integer?

Regards
   Klaus
- -- 
Klaus Ethgen                              http://www.ethgen.ch/
pub  4096R/4E20AF1C 2011-05-16   Klaus Ethgen <Klaus@???>
Fingerprint: 85D4 CA42 952C 949B 1753  62B3 79D0 B06F 4E20 AF1C