diff --git a/rtc_linux.c b/rtc_linux.c
index 6e1771b..8c4cec6 100644
--- a/rtc_linux.c
+++ b/rtc_linux.c
@@ -670,6 +670,7 @@ handle_relock_after_trim(void)
   time_t ref;
   double fast, slope;
 
+  valid = 0;
   run_regression(1, &valid, &ref, &fast, &slope);
 
   if (valid) {