diff --git a/docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md b/docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md
index 5ae40b57bd..851a927e8c 100644
--- a/docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md
+++ b/docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md
@@ -22,10 +22,10 @@ CURLOPT_ALTSVC_CTRL - control alt-svc behavior
 ~~~c
 #include <curl/curl.h>
 
-#define CURLALTSVC_READONLYFILE (1<<2)
-#define CURLALTSVC_H1           (1<<3)
-#define CURLALTSVC_H2           (1<<4)
-#define CURLALTSVC_H3           (1<<5)
+#define CURLALTSVC_READONLYFILE (1L<<2)
+#define CURLALTSVC_H1           (1L<<3)
+#define CURLALTSVC_H2           (1L<<4)
+#define CURLALTSVC_H3           (1L<<5)
 
 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC_CTRL, long bitmask);
 ~~~