1 files changed, 1 insertions, 1 deletions
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java b/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
index 4a49cd48..22f68b38 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
@@ -141,7 +141,7 @@ public class TypeInfos {
                 this.structSupertypes.getOrDefault(structType, P.orderedSet())
             );
         }
-        supertypes.plus(Types.TOP);
+        supertypes = supertypes.plus(Types.TOP);
         return supertypes;
     }