diff --git a/lib/util/hex.c b/lib/util/hex.c
index 653e733..2292bd7 100644
--- a/lib/util/hex.c
+++ b/lib/util/hex.c
@@ -84,7 +84,7 @@ hidrd_hex_buf_from_str(void        *buf,
 char *
 hidrd_hex_buf_to_str(const void *buf, size_t size)
 {
-    static const char   map[16] = "0123456789ABCDEF";
+    static const char   map[17] = "0123456789ABCDEF";
     const uint8_t      *bbuf    = (const uint8_t *)buf;
     char               *str;
     char               *p;