diff --git a/dust-lang/src/abstract_tree/logic.rs b/dust-lang/src/abstract_tree/logic.rs
index 9d181b2..1db1391 100644
--- a/dust-lang/src/abstract_tree/logic.rs
+++ b/dust-lang/src/abstract_tree/logic.rs
@@ -214,8 +214,8 @@ impl AbstractNode for Logic {
 
                 left_boolean || right_boolean
             }
-            Logic::Not(statement) => {
-                let boolean = run_and_expect_boolean(statement)?;
+            Logic::Not(expression) => {
+                let boolean = run_and_expect_boolean(expression)?;
 
                 !boolean
             }
diff --git a/dust-lang/src/value.rs b/dust-lang/src/value.rs
index 9520b79..01e305e 100644
--- a/dust-lang/src/value.rs
+++ b/dust-lang/src/value.rs
@@ -820,6 +820,8 @@ impl Function {
 
         debug!("Calling function");
 
+        self.body
+            .define_and_validate(&self.context, false, SourcePosition(0, usize::MAX))?;
         self.body
             .evaluate(&self.context, false, SourcePosition(0, usize::MAX))
     }
diff --git a/dust-lang/tests/functions.rs b/dust-lang/tests/functions.rs
index 82da220..11e4535 100644
--- a/dust-lang/tests/functions.rs
+++ b/dust-lang/tests/functions.rs
@@ -105,7 +105,7 @@ fn recursion() {
             	}
             }
 
-            fib(4)
+            fib(8)
             "
         ),
         Ok(Some(Value::integer(13)))