Bug with parsing ": pair in string

[d4mk0]

Hello guys! Today I seen something strange bug with exception:

Racc::ParseError: 
parse error on value ":" (":")

It was raised when I've tried call
PhpSerialization.load function with string argument like this 'a:2:{s:12:"my_attribute";s:17:"big city life "Berlin":)";}'

By PHP side this string decodes correctly.

ruby -v
ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin16]