diff --git a/src/main.rs b/src/main.rs
index 53b4d37..af0bd2f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -276,7 +276,7 @@ fn compile(code: &String, run_symbol: &String, output_filename: &Path) -> Result
 
     let signature = typedef::FunSignature {
         args: vec![],
-        ret: primitive.int32,
+        ret: primitive.none,
         vars: typedef::VarMap::new(),
     };
     let mut store = codegen::concrete_type::ConcreteTypeStore::new();
@@ -420,7 +420,7 @@ fn link_with_lld(elf_filename: &Path, obj_filename: &Path) -> Result<(), String>
     Ok(())
 }
 
-type RunFn = unsafe extern "C" fn() -> i32;
+type RunFn = unsafe extern "C" fn();
 
 struct CellBin {
     cell_id: usize,
@@ -470,13 +470,19 @@ struct Cell {
 }
 
 impl Cell {
+    const DEFAULT_CODE: &'static str = "def run():\n    pass";
+
     fn new() -> Self {
         Self {
-            code: "".to_string(),
+            code: Self::DEFAULT_CODE.to_string(),
             result: Err("".to_string()),
         }
     }
 
+    fn is_default(&self) -> bool {
+        self.code == Self::DEFAULT_CODE
+    }
+
     fn update(&mut self) {
         let mut new_bin = CellBin::new(0usize);
         self.result = new_bin
@@ -508,9 +514,13 @@ pub struct List {
 pub extern "C" fn __nac3_cells_plot(data: *const List) {
     let ui = unsafe { CELL_UI.as_mut().unwrap() };
     let data_slice = unsafe { std::slice::from_raw_parts((*data).data, (*data).length) };
-    let points: Vec<[f64; 2]> = (0..data_slice.len()).map(|i| [i as f64, data_slice[i]]).collect();
+    let points: Vec<[f64; 2]> = (0..data_slice.len())
+        .map(|i| [i as f64, data_slice[i]])
+        .collect();
     let line = egui_plot::Line::new(points);
-    egui_plot::Plot::new("my_plot").view_aspect(2.0).show(ui, |plot_ui| plot_ui.line(line));
+    egui_plot::Plot::new("my_plot")
+        .view_aspect(2.0)
+        .show(ui, |plot_ui| plot_ui.line(line));
 }
 
 impl Cells {
@@ -527,7 +537,8 @@ impl Cells {
     }
 
     fn ensure_last(&mut self) {
-        if self.cells.last().unwrap().result.is_ok() {
+        let last_cell = self.cells.last().unwrap();
+        if last_cell.result.is_ok() && !last_cell.is_default() {
             self.cells.push(Cell::new());
         }
     }
@@ -564,20 +575,13 @@ impl Cells {
                     );
                 });
                 match &cell.result {
-                    Ok(bin) => {
-                        let result = {
-                            unsafe {
-                                CELL_UI.replace(std::mem::transmute::<
-                                    &mut egui::Ui,
-                                    &'static mut egui::Ui,
-                                >(ui))
-                            };
-                            let result = unsafe { bin.run_fn.unwrap()() };
-                            unsafe { CELL_UI.take() };
-                            result
-                        };
-                        ui.label(format!("{}", result));
-                    }
+                    Ok(bin) => unsafe {
+                        CELL_UI.replace(
+                            std::mem::transmute::<&mut egui::Ui, &'static mut egui::Ui>(ui),
+                        );
+                        bin.run_fn.unwrap()();
+                        CELL_UI.take();
+                    },
                     Err(msg) => {
                         if !msg.is_empty() {
                             ui.colored_label(egui::Color32::from_rgb(255, 0, 0), msg);