diff --git a/docs/examples/httpput.c b/docs/examples/httpput.c
index 983e60240b160b16e04a7161ded707ee2888506a..ec80d3c9a347a3f1ab094d211eda16e07ad43c39 100644
--- a/docs/examples/httpput.c
+++ b/docs/examples/httpput.c
@@ -78,7 +78,8 @@ int main(int argc, char **argv)
     /* HTTP PUT please */
     curl_easy_setopt(curl, CURLOPT_PUT, TRUE);
 
-    /* specify target */
+    /* specify target URL, and note that this URL should include a file
+       name, not only a directory */
     curl_easy_setopt(curl,CURLOPT_URL, url);
 
     /* now specify which file to upload */