diff --git a/docs/libcurl/opts/CURLOPT_SHARE.md b/docs/libcurl/opts/CURLOPT_SHARE.md
index 2c6a496593..907e4f2805 100644
--- a/docs/libcurl/opts/CURLOPT_SHARE.md
+++ b/docs/libcurl/opts/CURLOPT_SHARE.md
@@ -43,6 +43,9 @@ if no share was used.
 
 Set this option to NULL again to stop using that share object.
 
+Warning: adding a *share* and then setting it to NULL while the transfer
+is ongoing is discouraged and may lead to undefined behavior.
+
 # DEFAULT
 
 NULL