diff --git a/lib/picotls.c b/lib/picotls.c
index e8b7ac0..b12a12c 100644
--- a/lib/picotls.c
+++ b/lib/picotls.c
@@ -6432,12 +6432,13 @@
 
 char *ptls_hexdump(char *dst, const void *_src, size_t len)
 {
+    char *buf = dst;
     const uint8_t *src = _src;
 
     for (size_t i = 0; i != len; ++i)
         dst = byte_to_hex(dst, src[i]);
     *dst = '\0';
-    return dst;
+    return buf;
 }
 
 char *ptls_jsonescape(char *buf, const char *unsafe_str, size_t len)