diff --git a/src/data_race.rs b/src/data_race.rs
index d249d28d03..097f5cdc90 100644
--- a/src/data_race.rs
+++ b/src/data_race.rs
@@ -597,7 +597,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
         // of the time, based on `rate`.
         let rate = this.machine.cmpxchg_weak_failure_rate;
         let cmpxchg_success = eq.to_scalar()?.to_bool()?
-            && (!can_fail_spuriously || this.machine.rng.get_mut().gen::<f64>() < rate);
+            && (!can_fail_spuriously || this.machine.rng.get_mut().gen::<f64>() >= rate);
         let res = Immediate::ScalarPair(
             old.to_scalar_or_uninit(),
             Scalar::from_bool(cmpxchg_success).into(),