diff --git a/modules/audio_output/audiounit_ios.m b/modules/audio_output/audiounit_ios.m
index f41336112fd3..d23d4131c190 100644
--- a/modules/audio_output/audiounit_ios.m
+++ b/modules/audio_output/audiounit_ios.m
@@ -602,6 +602,14 @@ static int role2policy_cmp(const void *key, const void *val)
             (long) [p_sys->avInstance outputNumberOfChannels],
             p_sys->b_spatial_audio_supported);
 
+    if (!p_sys->b_preferred_channels_set && fmt->i_channels > 2)
+    {
+        /* Ask the core to downmix to stereo if the preferred number of
+         * channels can't be set. */
+        fmt->i_physical_channels = AOUT_CHANS_STEREO;
+        aout_FormatPrepare(fmt);
+    }
+
     p_aout->current_sink_info.headphones = port_type == PORT_TYPE_HEADPHONES;
 
     p_sys->au_unit = au_NewOutputInstance(p_aout, kAudioUnitSubType_RemoteIO);