[Dovecot] assertion failed

[Tom Sommer]

Using test51:

Oct 22 23:37:21 one dovecot: 2657(ts at dreamcoder.dk): file 
mail-cache-fields.c: line 338 (mail_cache_header_fields_get): assertion 
failed: (buffer_get_used_size(dest) == sizeof(hdr) + (sizeof(uint32_t)*2 
+ 2) * hdr.fields_count)
Oct 22 23:37:21 one dovecot: child 2657 (imap) killed with signal 6

What does it mean?

--
Tom