diff --git a/docs/libcurl/opts/CURLOPT_CAINFO.3 b/docs/libcurl/opts/CURLOPT_CAINFO.3
index cb7f47b74f0515..85c9ba30ae0616 100644
--- a/docs/libcurl/opts/CURLOPT_CAINFO.3
+++ b/docs/libcurl/opts/CURLOPT_CAINFO.3
@@ -47,7 +47,8 @@ All TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
 .SH EXAMPLE
 TODO
 .SH AVAILABILITY
-If built TLS enabled
+For SSL engines that don't support certificate files the CURLOPT_CAINFO option
+is ignored. Refer to http://curl.haxx.se/docs/ssl-compared.html
 .SH RETURN VALUE
 Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or
 CURLE_OUT_OF_MEMORY if there was insufficient heap space.