diff --git a/src/main/java/io/usethesource/vallang/IListWriter.java b/src/main/java/io/usethesource/vallang/IListWriter.java
index f51f41b0..4095a419 100644
--- a/src/main/java/io/usethesource/vallang/IListWriter.java
+++ b/src/main/java/io/usethesource/vallang/IListWriter.java
@@ -23,6 +23,11 @@
  */
 public interface IListWriter extends IWriter<IList> {
 
+    @Override
+    public default IListWriter unique() {
+        return (IListWriter) IWriter.super.unique();
+    }
+
     /**
      * Inserts elements at a specific position, keeping the argument in order of appearance.
      *
diff --git a/src/main/java/io/usethesource/vallang/ISetWriter.java b/src/main/java/io/usethesource/vallang/ISetWriter.java
index d333b46c..8a43e016 100644
--- a/src/main/java/io/usethesource/vallang/ISetWriter.java
+++ b/src/main/java/io/usethesource/vallang/ISetWriter.java
@@ -13,5 +13,8 @@
 package io.usethesource.vallang;
 
 public interface ISetWriter extends IWriter<ISet> {
-
+    @Override
+    default ISetWriter unique() {
+        return (ISetWriter) IWriter.super.unique();
+    }
 }
diff --git a/src/main/java/io/usethesource/vallang/impl/persistent/ListWriter.java b/src/main/java/io/usethesource/vallang/impl/persistent/ListWriter.java
index 84b3f9db..2143e942 100644
--- a/src/main/java/io/usethesource/vallang/impl/persistent/ListWriter.java
+++ b/src/main/java/io/usethesource/vallang/impl/persistent/ListWriter.java
@@ -49,7 +49,7 @@ private ListWriter(boolean unique) {
     }
 
     @Override
-    public IWriter<IList> unique() {
+    public IListWriter unique() {
         return new ListWriter(true);
     }
 
@@ -239,4 +239,4 @@ public IList done() {
     public Supplier<IWriter<IList>> supplier() {
         return () -> new ListWriter();
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/io/usethesource/vallang/impl/reference/ListWriter.java b/src/main/java/io/usethesource/vallang/impl/reference/ListWriter.java
index 1ad939ea..8863099d 100644
--- a/src/main/java/io/usethesource/vallang/impl/reference/ListWriter.java
+++ b/src/main/java/io/usethesource/vallang/impl/reference/ListWriter.java
@@ -55,7 +55,7 @@ private ListWriter(boolean unique) {
     }
 
     @Override
-    public IWriter<IList> unique() {
+    public IListWriter unique() {
         return new ListWriter(true);
     }
 
diff --git a/src/main/java/io/usethesource/vallang/type/FunctionType.java b/src/main/java/io/usethesource/vallang/type/FunctionType.java
index b889e1e0..b557dfb8 100644
--- a/src/main/java/io/usethesource/vallang/type/FunctionType.java
+++ b/src/main/java/io/usethesource/vallang/type/FunctionType.java
@@ -268,7 +268,7 @@ public boolean isSubtypeOfFunction(Type other) {
         // For example, an overloadeded function `X f(int) + X f(str)` is substitutable at high-order parameter positions of type `X (int)`
         // even though its function type is `X (value)`. Rascal's type system does not check completeness of function definitions,
         // only _possible_ applicability in this manner. Every function may throw `CallFailed` at run-time
-        // if non of their arguments match for none of their alternatives.
+        // if non of their aguments match for none of their alternatives.
 
         FunctionType otherType = (FunctionType) other;