diff --git a/docs/intro.md b/docs/intro.md
index fc5a7b5..c5a5790 100644
--- a/docs/intro.md
+++ b/docs/intro.md
@@ -224,7 +224,7 @@ If the selected validator is not available or does not respond, the client can s
 
 The validators only confirm that the block hash of the block from which the requested information originates is correct. The consistency of the returned response cannot be checked in this way.
 
-Optionally, this information can be checked directly by the client. However, this is obligatory, but considerably increases safety. On the other hand, more information has to be transferred and a computationally complex check has to be performed by the client.
+Optionally, this information can be checked directly by the client. However, this is not obligatory, but considerably increases safety. On the other hand, more information has to be transferred and a computationally complex check has to be performed by the client.
 
 When a proof is requested, the node provides the Merkle Tree of the response so that the client can calculate and check the Merkle Root for the result itself.