diff --git a/flix.toml b/flix.toml
index 46ba6a7..292f606 100644
--- a/flix.toml
+++ b/flix.toml
@@ -1,6 +1,6 @@
 [package]
 name        = "ListSet"
 description = "A set that just requires equality."
-version     = "0.4.0"
+version     = "0.5.0"
 flix        = "0.53.0"
 authors     = ["Jonathan Lindegaard Starup"]
diff --git a/src/ListSet.flix b/src/ListSet.flix
index eb717c1..672dae1 100644
--- a/src/ListSet.flix
+++ b/src/ListSet.flix
@@ -215,17 +215,17 @@ mod ListSet {
     /// This is a linear time operation.
     ///
     pub def toString(s: ListSet[t]): String with ToString[t], Eq[t] = {
-        use StringBuilder.appendString!;
+        use StringBuilder.appendString;
         region rc {
             let sb = StringBuilder.empty(rc);
-            appendString!("ListSet(", sb);
+            appendString("ListSet(", sb);
             match extract(s) {
                 case hd :: tl =>
-                    appendString!("${hd}", sb);
-                    tl |> List.forEach(x -> appendString!(", ${x}", sb))
+                    appendString("${hd}", sb);
+                    tl |> List.forEach(x -> appendString(", ${x}", sb))
                 case Nil => ()
             };
-            appendString!(")", sb);
+            appendString(")", sb);
             StringBuilder.toString(sb)
         }
     }