diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c
index bedc889a80..4f6dcbe2ca 100644
--- a/libavcodec/j2kenc.c
+++ b/libavcodec/j2kenc.c
@@ -687,7 +687,8 @@ static void encode_cblk(Jpeg2000EncoderContext *s, Jpeg2000T1Context *t1, Jpeg20
     cblk->npasses = passno;
     cblk->ninclpasses = passno;
 
-    cblk->passes[passno-1].rate = ff_mqc_flush_to(&t1->mqc, cblk->passes[passno-1].flushed, &cblk->passes[passno-1].flushed_len);
+    if (passno)
+        cblk->passes[passno-1].rate = ff_mqc_flush_to(&t1->mqc, cblk->passes[passno-1].flushed, &cblk->passes[passno-1].flushed_len);
 }
 
 /* tier-2 routines: */