diff --git a/lib/event/reactor.c b/lib/event/reactor.c
index 69addc8bc2..b890f6e24e 100644
--- a/lib/event/reactor.c
+++ b/lib/event/reactor.c
@@ -908,7 +908,9 @@ _reactor_run(struct spdk_reactor *reactor)
 	 * tsc_last gets outdated. Update it to track
 	 * thread execution time correctly. */
 	if (spdk_unlikely(TAILQ_EMPTY(&reactor->threads))) {
-		reactor->tsc_last = spdk_get_ticks();
+		now = spdk_get_ticks();
+		reactor->idle_tsc += now - reactor->tsc_last;
+		reactor->tsc_last = now;
 		return;
 	}
 
diff --git a/test/unit/lib/event/reactor.c/reactor_ut.c b/test/unit/lib/event/reactor.c/reactor_ut.c
index eaeb381666..aaa1387442 100644
--- a/test/unit/lib/event/reactor.c/reactor_ut.c
+++ b/test/unit/lib/event/reactor.c/reactor_ut.c
@@ -382,7 +382,7 @@ test_reactor_stats(void)
 	 * Then,
 	 * - elapsed TSC of thread1 should be 2100 (= 2000+ 100).
 	 * - busy TSC of reactor should be 600 (= 500 + 100).
-	 * - idle TSC of reactor should be 500 (= 500 + 0).
+	 * - idle TSC of reactor should be 500 (= 500 + 900).
 	 */
 
 	MOCK_SET(spdk_env_get_current_core, 0);
@@ -494,7 +494,7 @@ test_reactor_stats(void)
 	CU_ASSERT(stats.idle_tsc == 0);
 
 	CU_ASSERT(reactor->busy_tsc == 600);
-	CU_ASSERT(reactor->idle_tsc == 500);
+	CU_ASSERT(reactor->idle_tsc == 1400);
 
 	/* 2000 + 100 = 2100 ticks elapsed */
 	CU_ASSERT(reactor->tsc_last == 2100);