diff --git a/dust-lang/src/disassembler.rs b/dust-lang/src/disassembler.rs
index 0a7be92..9c17e1d 100644
--- a/dust-lang/src/disassembler.rs
+++ b/dust-lang/src/disassembler.rs
@@ -353,7 +353,7 @@ impl<'a> Disassembler<'a> {
                     .indent(self.indent + 1)
                     .disassemble();
 
-                self.push_details(&function_disassembly);
+                self.output.push_str(&function_disassembly);
             }
         }
 
diff --git a/dust-lang/src/native_function.rs b/dust-lang/src/native_function.rs
index 80d5052..4cab885 100644
--- a/dust-lang/src/native_function.rs
+++ b/dust-lang/src/native_function.rs
@@ -52,6 +52,14 @@ macro_rules! define_native_function {
                     )*
                 }
             }
+
+            pub fn returns_value(&self) -> bool {
+                match self {
+                    $(
+                        NativeFunction::$name => $type.return_type.is_some(),
+                    )*
+                }
+            }
         }
 
         impl From<u8> for NativeFunction {
diff --git a/dust-lang/src/value.rs b/dust-lang/src/value.rs
index b39dc83..b6d2db2 100644
--- a/dust-lang/src/value.rs
+++ b/dust-lang/src/value.rs
@@ -344,6 +344,22 @@ impl Display for Value {
     }
 }
 
+/// Value representation that can be resolved to a concrete value by the VM.
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+pub enum AbstractValue {
+    List { start: u8, end: u8, item_type: Type },
+}
+
+impl Display for AbstractValue {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            AbstractValue::List { start, end, .. } => {
+                write!(f, "List [R{}..=R{}]", start, end)
+            }
+        }
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
 pub enum ConcreteValue {
     Boolean(bool),
@@ -714,22 +730,6 @@ impl Ord for RangeValue {
     }
 }
 
-/// Value representation that can be resolved to a concrete value by the VM.
-#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
-pub enum AbstractValue {
-    List { start: u8, end: u8, item_type: Type },
-}
-
-impl Display for AbstractValue {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match self {
-            AbstractValue::List { start, end, .. } => {
-                write!(f, "List [R{}..=R{}]", start, end)
-            }
-        }
-    }
-}
-
 #[derive(Clone, Debug, PartialEq)]
 pub enum ValueError {
     CannotAdd(Value, Value),