diff --git a/lib/libwebsockets.c b/lib/libwebsockets.c
index af77b3a8..9c9d2714 100644
--- a/lib/libwebsockets.c
+++ b/lib/libwebsockets.c
@@ -2084,13 +2084,10 @@ lws_partial_buffered(struct lws *wsi)
 	return !!wsi->trunc_len;
 }
 
-LWS_VISIBLE size_t
+LWS_VISIBLE lws_fileofs_t
 lws_get_peer_write_allowance(struct lws *wsi)
 {
-	if (wsi->role_ops->tx_credit)
-		return wsi->role_ops->tx_credit(wsi);
-
-	return -1;
+	return wsi->role_ops->tx_credit(wsi);
 }
 
 LWS_VISIBLE void
diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index a0c63e1f..f452e3d4 100644
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -5208,7 +5208,7 @@ lws_get_socket_fd(struct lws *wsi);
  * automatically, so this number reflects the situation at the peer or
  * intermediary dynamically.
  */
-LWS_VISIBLE LWS_EXTERN size_t
+LWS_VISIBLE LWS_EXTERN lws_fileofs_t
 lws_get_peer_write_allowance(struct lws *wsi);
 ///@}
 
diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index 1985e0b4..54700b7c 100644
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -550,7 +550,7 @@ struct lws_role_ops {
 	/* do effective callback on writeable */
 	int (*callback_on_writable)(struct lws *wsi);
 	/* connection-specific tx credit in bytes */
-	lws_filepos_t (*tx_credit)(struct lws *wsi);
+	lws_fileofs_t (*tx_credit)(struct lws *wsi);
 	/* role-specific write formatting */
 	int (*write_role_protocol)(struct lws *wsi, unsigned char *buf,
 				   size_t len, enum lws_write_protocol *wp);
diff --git a/lib/roles/h2/ops-h2.c b/lib/roles/h2/ops-h2.c
index 47bbaff1..51ac1428 100644
--- a/lib/roles/h2/ops-h2.c
+++ b/lib/roles/h2/ops-h2.c
@@ -486,7 +486,7 @@ rops_init_context_h2(struct lws_context *context,
 	return 0;
 }
 
-static lws_filepos_t
+static lws_fileofs_t
 rops_tx_credit_h2(struct lws *wsi)
 {
 	return lws_h2_tx_cr_get(wsi);