diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/lib/ClassInstanceValue.java b/ownlang-parser/src/main/java/com/annimon/ownlang/lib/ClassInstanceValue.java
index 9a2ff76..3def100 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/lib/ClassInstanceValue.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/lib/ClassInstanceValue.java
@@ -40,7 +40,9 @@ public class ClassInstanceValue implements Value {
 
     public void callConstructor(Value[] args) {
         if (constructor != null) {
+            CallStack.enter("class " + className, constructor, null);
             constructor.execute(args);
+            CallStack.exit();
         }
     }
 
@@ -64,18 +66,18 @@ public class ClassInstanceValue implements Value {
 
     @Override
     public int asInt() {
-        throw new TypeException("Cannot cast class to integer");
+        throw new TypeException("Cannot cast class " + className + " to integer");
     }
 
     @Override
     public double asNumber() {
-        throw new TypeException("Cannot cast class to integer");
+        throw new TypeException("Cannot cast class " + className + " to number");
     }
 
     @Override
     public String asString() {
         if (toString != null) {
-            return toString.execute(new Value[] {}).asString();
+            return toString.execute(new Value[0]).asString();
         }
         return className + "@" + thisMap;
     }