diff --git a/libavcodec/j2kdec.c b/libavcodec/j2kdec.c
index 73af6a73df1bb97a39a20f514b3c094cd79f8f52..998752be1c3260516e0e2a27dbf7323e098e85ab 100644
--- a/libavcodec/j2kdec.c
+++ b/libavcodec/j2kdec.c
@@ -701,9 +701,9 @@ static int decode_cblk(J2kDecoderContext *s, J2kCodingStyle *codsty, J2kT1Contex
     for (y = 0; y < height; y++)
         memset(t1->data[y], 0, width*sizeof(int));
 
-    ff_mqc_initdec(&t1->mqc, cblk->data);
     cblk->data[cblk->length] = 0xff;
     cblk->data[cblk->length+1] = 0xff;
+    ff_mqc_initdec(&t1->mqc, cblk->data);
 
     while(passno--){
         switch(pass_t){