diff --git a/README.adoc b/README.adoc
index e54342e..1c7f408 100644
--- a/README.adoc
+++ b/README.adoc
@@ -19,7 +19,7 @@ WARNING: UNDER DEVELOPMENT
 
 - `io.emeraldpay.polkaj:polkaj-scale:{lib-version}` - SCALE codec implementation
 - `io.emeraldpay.polkaj:polkaj-scale-types:{lib-version}` - SCALE mapping for standard Polkadot types
-- `io.emeraldpay.polkaj:polkaj-schnorrkel:{lib-version}` - Schnorrkel for Java
+- `io.emeraldpay.polkaj:polkaj-schnorrkel:{lib-version}` *1 - Schnorrkel for Java
 - `io.emeraldpay.polkaj:polkaj-ss58:{lib-version}` - SS58 codec to encode/decode addresses and pubkeys
 - `io.emeraldpay.polkaj:polkaj-common-types:{lib-version}` - common types (Address, DotAmount, Hash256, etc)
 - `io.emeraldpay.polkaj:polkaj-json-types:{lib-version}` - JSON RPC mapping to Java classes
@@ -28,6 +28,8 @@ WARNING: UNDER DEVELOPMENT
 - `io.emeraldpay.polkaj:polkaj-api-ws:{lib-version}` - JSON RPC WebSocket client
 - `io.emeraldpay.polkaj:polkaj-tx:{lib-version}` - Storage access and Extrinsics
 
+*1 module requires `cargo` (rust build tool)
+
 == Usage
 
 To use development SNAPSHOT versions you need to install the library into the local Maven repository.
@@ -85,4 +87,4 @@ client.close();
 
 The core project code is released under Apache 2.0 license.
 
-Examples and docs are published under CC0 license + additionally Apache 2.0 for code parts in the examples.
\ No newline at end of file
+Examples and docs are published under CC0 license + additionally Apache 2.0 for code parts in the examples.