diff --git a/audio/out/pull.c b/audio/out/pull.c
index a4aa53821e..c6125bd8bc 100644
--- a/audio/out/pull.c
+++ b/audio/out/pull.c
@@ -153,8 +153,8 @@ int ao_read_data(struct ao *ao, void **data, int samples, int64_t out_time_us)
     int buffered_bytes = mp_ring_buffered(p->buffers[0]);
     bytes = MPMIN(buffered_bytes, full_bytes);
 
-    if (buffered_bytes < bytes && !atomic_load(&p->draining))
-        atomic_fetch_add(&p->underflow, (bytes - buffered_bytes) / ao->sstride);
+    if (full_bytes > bytes && !atomic_load(&p->draining))
+        atomic_fetch_add(&p->underflow, (full_bytes - bytes) / ao->sstride);
 
     if (bytes > 0)
         atomic_store(&p->end_time_us, out_time_us);