diff --git a/include/haproxy/buf.h b/include/haproxy/buf.h
index 3f45ee849..4ea4b73f1 100644
--- a/include/haproxy/buf.h
+++ b/include/haproxy/buf.h
@@ -913,7 +913,7 @@ static inline int b_peek_varint(struct buffer *b, size_t ofs, uint64_t *vptr)
 	uint64_t v = 0;
 	int bits = 0;
 
-	BUG_ON_HOT(ofs > data);
+	BUG_ON_HOT(ofs > b_data(b));
 
 	if (data != 0 && (*head >= 0xF0)) {
 		v = *head;