diff --git a/broker/JFJochStateMachine.cpp b/broker/JFJochStateMachine.cpp
index 29ee052d0..ccadf4949 100644
--- a/broker/JFJochStateMachine.cpp
+++ b/broker/JFJochStateMachine.cpp
@@ -85,6 +85,8 @@ bool JFJochStateMachine::CalibrateJUNGFRAU(std::unique_lock<std::mutex> &ul) {
 
 void JFJochStateMachine::CalibrateDetector(std::unique_lock<std::mutex> ul) {
     cancel_sequence = false;
+    // Status and messages must not show the previous run's prefix; calibration writes no files anyway
+    experiment.FilePrefix("");
 
     pixel_mask = PixelMask(experiment);
     UpdatePixelMaskStatistics(pixel_mask.GetStatistics());