diff --git a/libavcodec/dpx.c b/libavcodec/dpx.c
index cbddfa4043..6ef2db2299 100644
--- a/libavcodec/dpx.c
+++ b/libavcodec/dpx.c
@@ -114,7 +114,7 @@ static int decode_frame(AVCodecContext *avctx,
                    avctx->sample_aspect_ratio.num,  avctx->sample_aspect_ratio.den,
                   0x10000);
     else
-        avctx->sample_aspect_ratio = (AVRational){ 0, 0 };
+        avctx->sample_aspect_ratio = (AVRational){ 0, 1 };
 
     switch (descriptor) {
         case 51: // RGBA