diff --git a/module/zfs/lz4.c b/module/zfs/lz4.c
index 800635b34..75a31bf17 100644
--- a/module/zfs/lz4.c
+++ b/module/zfs/lz4.c
@@ -541,7 +541,7 @@ LZ4_decompress_generic(
                  const size_t dictSize         /* note : = 0 if noDict */
                  )
 {
-    if (src == NULL) { return -1; }
+    if ((src == NULL) || (outputSize < 0)) { return -1; }
 
     {   const BYTE* ip = (const BYTE*) src;
         const BYTE* const iend = ip + srcSize;