diff --git a/docs/libcurl/opts/CURLOPT_PROXYAUTH.md b/docs/libcurl/opts/CURLOPT_PROXYAUTH.md
index a0df997aac..aff0dde6ab 100644
--- a/docs/libcurl/opts/CURLOPT_PROXYAUTH.md
+++ b/docs/libcurl/opts/CURLOPT_PROXYAUTH.md
@@ -67,6 +67,11 @@ int main(void)
 }
 ~~~
 
+# HISTORY
+
+CURLAUTH_\* macros became `long` types in 7.26.0, prior to this version
+a `long` cast is necessary when passing to curl_easy_setopt(3).
+
 # %AVAILABILITY%
 
 # RETURN VALUE