diff --git a/apps/codecs/mp3_enc.c b/apps/codecs/mp3_enc.c
index 20f5932576..d04b9e6c42 100644
--- a/apps/codecs/mp3_enc.c
+++ b/apps/codecs/mp3_enc.c
@@ -2091,12 +2091,12 @@ STATICIRAM void to_mono_mm(void)
      * |mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
      */
     uint16_t *samp = &mfbuf[2*512];
-    uint16_t *samp_end = samp + samp_per_frame;
+    uint16_t *samp_end = samp + 2*samp_per_frame;
 
     inline void to_mono(uint16_t **samp)
     {
-        int16_t l = **samp;
-        int16_t r = **(samp+1);
+        int16_t r = **samp;
+        int16_t l = *(*samp+1);
         int32_t m;
 
         switch(cfg.rec_mono_mode)