The age people become eligible for free bus passes in Wales is to rise from 60 to the state pension age under Welsh Government plans.Ministers are concerned at the rising cost of the pass, with 880,000 people expected to be eligible by 2021.
Transport Minister Ken Skates confirmed the move, to be introduced gradually, will be included in a proposed new law.
But the Older Person's Commissioner is concerned about the potential impact on the most vulnerable older people.
The state pension age for men and women is 65 and will rise to 67 by 2028.
Details of when the changes will be introduced remain sketchy. The pass, introduced in 2002, entitles users to free bus travel.
According to a recent consultation, pass-holders represent about 47% of bus journeys in Wales.
There were about 730,000 passes in circulation at the end of last year
Bus firms are reimbursed on the basis of an adult single fare, according to a White Paper published last year. Figures from 2016 show the cost of providing free bus travel up to then was in the region of £840m.
The White Paper that put the proposals to consultation said the cost to the public purse was "rising" and the Welsh Government "needs to consider ways of managing the rising costs without affecting the eligibility of those persons currently entitled to a concessionary pass".
It said the way reimbursement works was not an incentive for operators to keep fares low.
The consultation proposed introducing the change incrementally and in a way that means anyone who holds a pass at the time of the changes will be completely unaffected.
In a statement to AMs, Mr Skates said the bill would "amend the eligibility for the mandatory concessionary fares scheme so that over time it will align with a person's state pension age".Older People's Commissioner Heléna Herklots said although details were limited, she was "concerned the changes could have a significant impact on many older people".
"Many bus services in Wales have been lost in recent years, with many more currently under threat, and a reduction in the number of users on less popular routes, many of whom will be older people, is likely to further exacerbate this," she said.
"More importantly, increasing the eligibility age will undoubtedly affect some of the most vulnerable older people in Wales, such as those living in poverty or near the poverty line, people who have given up work to care for loved ones and those living with long-term health conditions."
A Welsh Government spokesman said: "We remain committed to the principles which have underpinned the scheme in Wales for more than a decade - providing older and disabled people, and more recently some veterans and service personnel, universal access to free bus travel anywhere in Wales on local scheduled bus services.
"Changes to the eligibility age will be phased in and we will ensure that universal entitlement is retained. Any person who holds a concessionary pass at the time the changes to the law are made will be completely unaffected."
Others who receive passes would be unaffected.
I imagine m that this will a stealth increase and it will be done in such a way that it will not be blatantly obvious.
Evert European country seem to be intent on raising the retirement age as we live longer and are more active than previous generations.
But we should acknowledge that there is a difference, between an Office Worker and a Labourer working in to their late sixties, and this is the sort of debate we should be having.
Bearing in mind older people are more likely to vote it remains that it will be a brave move to rise the bus pas entitlement age and may not be very wise.