diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index 2ae1df58939d..9014c814a00a 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -3528,6 +3528,8 @@ void ext_server_init(struct rq *rq)
  *
  * When ops.core_sched_before() is enabled, @p->scx.core_sched_at is used to
  * implement FIFO ordering within each local DSQ. See pick_task_scx().
+ *
+ * Return: %true if @a should run after @b.
  */
 bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 		   bool in_fi)
@@ -3536,6 +3538,10 @@ bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 	struct scx_sched *sch_b = scx_task_sched(b);
 
 	/*
+	 * scx_prio_less() returns whether @a should run after @b while
+	 * ops.core_sched_before() returns whether its first argument should run
+	 * before the second. Swap the arguments.
+	 *
 	 * The const qualifiers are dropped from task_struct pointers when
 	 * calling ops.core_sched_before(). Accesses are controlled by the
 	 * verifier.
@@ -3544,8 +3550,8 @@ bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 	    !scx_bypassing(sch_a, task_cpu(a)))
 		return SCX_CALL_OP_2TASKS_RET(sch_a, core_sched_before,
 					      task_rq(a),
-					      (struct task_struct *)a,
-					      (struct task_struct *)b);
+					      (struct task_struct *)b,
+					      (struct task_struct *)a);
 	else
 		return time_after64(a->scx.core_sched_at, b->scx.core_sched_at);
 }
diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index dd0434437835..723f45fe0cbc 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -900,7 +900,7 @@ static s64 task_qdist(struct task_struct *p)
 bool BPF_STRUCT_OPS(qmap_core_sched_before,
 		    struct task_struct *a, struct task_struct *b)
 {
-	return task_qdist(a) > task_qdist(b);
+	return task_qdist(a) < task_qdist(b);
 }
 
 /*