diff --git a/core/sound/ym3438.c b/core/sound/ym3438.c
index 8a9d328..5dd8b42 100644
--- a/core/sound/ym3438.c
+++ b/core/sound/ym3438.c
@@ -42,6 +42,7 @@
  * version: 1.0.2
  */
 
+#include <string.h>
 #include "ym3438.h"
 
 enum {
diff --git a/core/sound/ym3438.h b/core/sound/ym3438.h
index 3ba0846..1f44ec7 100644
--- a/core/sound/ym3438.h
+++ b/core/sound/ym3438.h
@@ -45,7 +45,7 @@
 #ifndef YM3438_H
 #define YM3438_H
 
-#include <inttypes.h>
+#include <stdint.h>
 
 typedef uintptr_t       Bitu;
 typedef intptr_t        Bits;
diff --git a/libretro/libretro.c b/libretro/libretro.c
index de1dd55..b6e3ccf 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -1032,7 +1032,16 @@ static void check_variables(void)
       }
     }
   }
-	
+
+  var.key = "genesis_plus_gx_sound_output";
+  environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
+  {
+    if (!strcmp(var.value, "mono"))
+      config.mono = 1;
+    else if (!strcmp(var.value, "stereo"))
+      config.mono = 0; 
+  }
+
   var.key = "genesis_plus_gx_audio_filter";
   environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
   {
@@ -1646,12 +1655,12 @@ void retro_set_environment(retro_environment_t cb)
       { "genesis_plus_gx_lock_on", "Cartridge lock-on; disabled|game genie|action replay (pro)|sonic & knuckles" },
       { "genesis_plus_gx_ym2413", "Master System FM; auto|disabled|enabled" },
       { "genesis_plus_gx_dac_bits", "YM2612 DAC quantization; disabled|enabled" },
-
       #ifdef HAVE_YM3438_CORE
       { "genesis_plus_gx_ym3438", "YM2612/YM3438 core; mame|nuked opn2" },
       #endif
 
       { "genesis_plus_gx_audio_filter", "Audio filter; disabled|low-pass" },
+      { "genesis_plus_gx_sound_output", "Sound output; stereo|mono" }, 
       { "genesis_plus_gx_lowpass_range", "Low-pass filter %; 60|65|70|75|80|85|90|95|5|10|15|20|25|30|35|40|45|50|55"},
       
       #if HAVE_EQ