diff --git a/libavcodec/ppc/mpegvideo_altivec.c b/libavcodec/ppc/mpegvideo_altivec.c
index ce53ae4b61..1b6bda6c36 100644
--- a/libavcodec/ppc/mpegvideo_altivec.c
+++ b/libavcodec/ppc/mpegvideo_altivec.c
@@ -42,8 +42,6 @@ static void dct_unquantize_h263_altivec(MpegEncContext *s,
     int i, level, qmul, qadd;
     int nCoeffs;
 
-    assert(s->block_last_index[n]>=0);
-
     qadd = (qscale - 1) | 1;
     qmul = qscale << 1;
 
@@ -59,6 +57,7 @@ static void dct_unquantize_h263_altivec(MpegEncContext *s,
         nCoeffs= 63; //does not always use zigzag table
     } else {
         i = 0;
+        av_assert2(s->block_last_index[n]>=0);
         nCoeffs= s->intra_scantable.raster_end[ s->block_last_index[n] ];
     }