The ability to adapt our locomotion in a feedforward (i.e., 'predictive') manner is crucial for safe and efficient walking behaviour. Equally important is the ability to quickly de-adapt and update behaviour that is no longer appropriate for the given context. It has been suggested that anxiety induced via postural threat may play a fundamental role in disrupting such de-adaptation. We tested this hypothesis, using the 'broken escalator' phenomenon: Fifty-six healthy young adults walked onto a stationary walkway ('BEFORE' condition, five trials), then onto a moving walkway akin to an airport travellator ('MOVING' condition, 10 trials) and then again onto the stationary walkway ('AFTER' condition, five trials). Participants completed all trials whilst wearing a virtual reality headset, which was used to induce postural threat-related anxiety (raised cliff-like drop at the end of the walkway) during different phases of the paradigm. We found that performing the locomotor adaptation phase in a state of increased threat disrupted subsequent de-adaptation during AFTER trials: These participants displayed anticipatory muscular activity as if expecting the platform to move, and exhibited inappropriate anticipatory forward trunk movement that persisted during multiple AFTER trials. In contrast, postural threat induced during AFTER trials did not affect behavioural or neurophysiological outcomes. These findings highlight that actions learned in the presence of postural threat-induced anxiety are strengthened, leading to difficulties de-adapting these behaviours when no longer appropriate. Given the associations between anxiety and persistent maladaptive gait behaviours (e.g., 'overly-cautious' gait, functional gait disorders), findings have implications for the understanding of such conditions.