diff --git a/connector/c/include/tp.h b/connector/c/include/tp.h
index 808955dd0f66cd0d32cc7c5f00121c948bee4ee5..444cb13e0c8ee0fa391c2453f46658da72f3f323 100644
--- a/connector/c/include/tp.h
+++ b/connector/c/include/tp.h
@@ -499,7 +499,7 @@ tp_reqbuf(char *buf, size_t size) {
 
 static inline ssize_t
 tp_req(struct tp *p) {
-	return tp_reqbuf(p->s, tp_used(p));
+	return tp_reqbuf(p->s, tp_size(p));
 }
 
 static inline size_t