diff --git a/docs/libcurl/opts/CURLOPT_ALTSVC.3 b/docs/libcurl/opts/CURLOPT_ALTSVC.3
index a13edaae8..8c7ab60a6 100644
--- a/docs/libcurl/opts/CURLOPT_ALTSVC.3
+++ b/docs/libcurl/opts/CURLOPT_ALTSVC.3
@@ -39,6 +39,8 @@ Pass in a pointer to a \fIfilename\fP to instruct libcurl to use that file as
 the Alt-Svc cache to read existing cache contents from and possibly also write
 it back to a after a transfer, unless \fBCURLALTSVC_READONLYFILE\fP is set in
 \fICURLOPT_ALTSVC_CTRL(3)\fP.
+
+Specify a blank file name ("") to make libcurl not load from a file at all.
 .SH DEFAULT
 NULL. The alt-svc cache is not read nor written to file.
 .SH PROTOCOLS