diff --git a/docs/libcurl/curl_multi_timeout.3 b/docs/libcurl/curl_multi_timeout.3
index b04acf89033e4e1b483ef148faefe39eaaa39578..fbdb8fb039259093b05acd16fcf1537f0570272e 100644
--- a/docs/libcurl/curl_multi_timeout.3
+++ b/docs/libcurl/curl_multi_timeout.3
@@ -23,6 +23,10 @@ The timeout value returned in the long \fBtimeout\fP points to, is in number
 of milliseconds at this very moment. If 0, it means you should proceed
 immediately without waiting for anything. If it returns -1, there's no timeout
 at all set.
+
+Note: if libcurl returns a -1 timeout here, it just means that libcurl
+currently has no stored timeout value. You must not wait too long (more than a
+few seconds perhaps) before you call curl_multi_perform() again.
 .SH "RETURN VALUE"
 The standard CURLMcode for multi interface error codes.
 .SH "TYPICAL USAGE"