diff --git a/usvm-ts/src/main/kotlin/org/usvm/TSTypeStorage.kt b/usvm-ts/src/main/kotlin/org/usvm/TSTypeStorage.kt
index 07491f0fc..22878ab17 100644
--- a/usvm-ts/src/main/kotlin/org/usvm/TSTypeStorage.kt
+++ b/usvm-ts/src/main/kotlin/org/usvm/TSTypeStorage.kt
@@ -6,6 +6,10 @@ import org.jacodb.ets.base.EtsType
     This is a very basic implementation of type storage with memory and model objects interoperability.
     Currently, supports only stack register readings, but API-wise is finished.
 
+    Each untyped ref entity (reg reading, etc.) must define its own way to generate a key.
+    For reg readings it is suggested to use its 'idx' field since
+    they are sustained among all models and symbolic memory.
+
     TODO: support other possibly untyped refs.
  */
 class TSTypeStorage(