A coroner has called for safety improvements after an 18-year-old plunged to his death from Pontcysyllte Aqueduct in 2016.
Kristopher McDowell, of Wrexham, fell when a railing came away as he climbed onto the exterior of the parapet.
Coroner John Gittins said he felt testing procedures ensuring the upright posts were fully engaged at all times were "inadequate."
He raised concerns in a prevention of future deaths report.
The jury at an inquest into Mr McDowell's death recorded a conclusion of misadventure on Wednesday.
Mr McDowell was holding onto an upright rail when it gave way and he fell 37m (120 ft).
Mr Gittins said he was uneasy that an annual "push/pull" test - which sees force exerted on the posts by inspectors - could lead to inconsistencies in information.
The coroner also expressed concern that signage alone did not provide adequate warning of risk. A gap in the railings of 195 millimetres was larger than current British standards of 110m.
This was a particular issue if people deliberately intended to cross to the outer edge of the aqueduct like Mr McDowell, the coroner said.
The Canal and River Trust has 56 days to inform the coroner of its response to the report.