diff --git a/docs/docs/upgrading.md b/docs/docs/upgrading.md
index f9d5e14ce..63886a931 100644
--- a/docs/docs/upgrading.md
+++ b/docs/docs/upgrading.md
@@ -13,6 +13,23 @@ description: >-
 
 With this release, default log level has been changed to INFO.
 
+### HTTP 1.0
+
+HTTP 1.0 is not supported anymore. If you relied on it make sure to upgrade to HTTP 1.1 or higher.
+
+Example for HAProxy health check, in pre `0.9.0`:
+
+```shell script
+option httpchk GET /ping
+```
+
+In `0.9.0`:
+
+```shell script
+
+option httpchk GET /ping HTTP/1.1\r\nHost:pomerium
+```
+
 # Since 0.8.0
 
 ## Breaking