diff --git a/vpx/src/vpx_decoder.c b/vpx/src/vpx_decoder.c
index 276238b..a90fe95 100644
--- a/vpx/src/vpx_decoder.c
+++ b/vpx/src/vpx_decoder.c
@@ -119,7 +119,7 @@
 
   /* Sanity checks */
   /* NULL data ptr allowed if data_sz is 0 too */
-  if (!ctx || (!data && data_sz))
+  if (!ctx || (!data && data_sz) || (data && !data_sz))
     res = VPX_CODEC_INVALID_PARAM;
   else if (!ctx->iface || !ctx->priv)
     res = VPX_CODEC_ERROR;