diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt
index 7088f8af1c3..46590880c94 100644
--- a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt
@@ -172,6 +172,11 @@ var <D : FirCallableDeclaration>
 
 private object InitialSignatureKey : FirDeclarationDataKey()
 
+/**
+ * Some Java declarations are renamed (CharSequence.charAt) or have signatures with erased (Object) value parameters (Collection.remove).
+ *
+ * When the receiver is a mapped declaration with a Kotlin signature, this property returns the declaration with the initial Java signature.
+ */
 var FirCallableDeclaration.initialSignatureAttr: FirCallableDeclaration? by FirDeclarationDataRegistry.data(InitialSignatureKey)
 
 private object MatchingParameterFunctionTypeKey : FirDeclarationDataKey()