Psychological inoculations are hailed as one of the most promising evidence-based techniques to preemptively protect public support against negative information and events, especially in time-sensitive domains like climate change mitigation and energy transitions. However, field testing of these techniques is limited, and their ecological validity thus remains to be investigated. In Fall 2021, a prospecting campaign for geothermal exploration in Geneva, Switzerland deployed seismic trucks at night that created noise and seismic vibrations which could negatively affect public support for geothermal energy systems. Here, we employed a trust inoculation in a preregistered, longitudinal field study, to make the trustworthiness of the responsible utility company salient to protect public support of geothermal energy systems against this local negative event. Contrary to our expectations, we found no evidence that the event affected participants’ public support towards renewable energy, nor that the trust inoculation influenced said support. This could have been due to the unintended negative influence of the time delay between the delivery of the trust inoculation and the negative event, as the inoculation was more effective with the longest time delay between its delivery and the negative event, but had unintended negative consequences with the shortest delay. We conclude by placing these results in the growing psychological inoculations literature and providing recommendations for future field studies for psychological inoculations.