diff --git a/docs/KNOWN_BUGS b/docs/KNOWN_BUGS
index df85490ffcd4b07404710e1a1c21567b7cdb9b39..bf9f2bfd3791c31fe6997902b0e9a5c78b216a54 100644
--- a/docs/KNOWN_BUGS
+++ b/docs/KNOWN_BUGS
@@ -3,6 +3,10 @@ join in and help us correct one or more of these! Also be sure to check the
 changelog of the current development status, as one or more of these problems
 may have been fixed since this was written!
 
+* Doing resumed upload over HTTP does not work with '-C -', because curl
+  doesn't do a HEAD first to get the initial size. This needs to be done
+  manually for HTTP PUT resume to work, and then '-C [index]'.
+
 * CURLOPT_USERPWD and CURLOPT_PROXYUSERPWD have no way of providing user names
   that contain a colon. This can't be fixed easily in a backwards compatible
   way without adding new options (and then, they should most probably allow