diff --git a/lib/sendf.h b/lib/sendf.h
index 7b6cff7de18271162cfb56f3088f175773432b20..67248108e7be6c680730aaf98995e2cb705a5bb9 100644
--- a/lib/sendf.h
+++ b/lib/sendf.h
@@ -51,6 +51,6 @@ int Curl_read(struct connectdata *conn, int sockfd,
 /* internal write-function, does plain socket, SSL and krb4 */
 CURLcode Curl_write(struct connectdata *conn, int sockfd,
                     void *mem, size_t len,
-                    size_t *written);
+                    ssize_t *written);
 
 #endif