Comment # 13 on bug 915037 from Dr. Werner Fink

Ahhh  ... why there is no colon at the end of this string?  The default value
is

   "'><=;|&(:

that is *with* colon at the end.  I'm aware that colon is a problem with osc
nevertheless and even with the FAQ of the bash

  [...]
  The current set of completion word break characters is available in bash as
  the value of the COMP_WORDBREAKS variable.  Removing `:' from that value is
  enough to make the colon not special to completion:

  COMP_WORDBREAKS=${COMP_WORDBREAKS//:}
  [...]

the colon is special if used with bash completion.