diff --git a/libavcodec/mace.c b/libavcodec/mace.c
index a104fb04ed..be50d3d94f 100644
--- a/libavcodec/mace.c
+++ b/libavcodec/mace.c
@@ -410,18 +410,18 @@ static int mace_decode_frame(AVCodecContext *avctx,
 #ifdef DEBUG
 puts("mace_decode_frame[3]()");
 #endif
-        Exp1to3(c, buf, samples, buf_size / 2, avctx->channels, 1);
+        Exp1to3(c, buf, samples, buf_size / 2 / avctx->channels, avctx->channels, 1);
         if (avctx->channels == 2)
-            Exp1to3(c, buf, samples+1, buf_size / 2, 2, 2);
+            Exp1to3(c, buf, samples+1, buf_size / 2 / 2, 2, 2);
         *data_size = 2 * 3 * buf_size;
         break;
     case CODEC_ID_MACE6:
 #ifdef DEBUG
 puts("mace_decode_frame[6]()");
 #endif
-        Exp1to6(c, buf, samples, buf_size, avctx->channels, 1);
+        Exp1to6(c, buf, samples, buf_size / avctx->channels, avctx->channels, 1);
         if (avctx->channels == 2)
-            Exp1to6(c, buf, samples+1, buf_size, 2, 2);
+            Exp1to6(c, buf, samples+1, buf_size / 2, 2, 2);
         *data_size = 2 * 6 * buf_size;
         break;
     default: