diff --git a/src/app/logic/calc.rs b/src/app/logic/calc.rs
index 5fdadb9..f430b64 100644
--- a/src/app/logic/calc.rs
+++ b/src/app/logic/calc.rs
@@ -81,7 +81,7 @@ impl Grid {
     /// Save file to `path` as a csv. Path with have `csv` appended to it if it
     /// does not already have the extension.
     pub fn save_to(&mut self, path: impl Into<PathBuf>) -> std::io::Result<()> {
-        let path = path.into();
+        let mut path = path.into();
 
         let resolve_values;
 
@@ -94,13 +94,15 @@ impl Grid {
                     resolve_values = false;
                 }
                 _ => {
-                    resolve_values = false;
-                    // path.add_extension(CUSTOM_EXT);
+                    // File as an extension but isn't ours.
+                    // Save as csv-like
+                    resolve_values = true;
                 }
             },
             None => {
+                // File has no extension. Save it as our file type
                 resolve_values = false;
-                // path.add_extension(CUSTOM_EXT);
+                path.add_extension(CUSTOM_EXT);
             }
         }
 
@@ -543,8 +545,8 @@ fn saving_neoscim() {
     assert_eq!(cell.escaped_csv_string(), "=A10^2");
 
     // set saving the file
-    let filename=  "/tmp/file.neoscim";
-    app.grid.save_to(filename).expect("This will only work on linux systems");
+    let filename = format!("/tmp/file.{CUSTOM_EXT}");
+    app.grid.save_to(&filename).expect("This will only work on linux systems");
     let mut file = fs::OpenOptions::new().read(true).open(filename).expect("Just wrote the file");
     let mut buf = String::new();
     file.read_to_string(&mut buf).expect("Just opened the file");
diff --git a/src/app/mode.rs b/src/app/mode.rs
index c28f8ef..c589c60 100644
--- a/src/app/mode.rs
+++ b/src/app/mode.rs
@@ -70,25 +70,11 @@ impl Mode {
                 "w" => {
                     // first try the passed argument as file
                     if let Some(arg) = args.get(1) {
-                        let mut path: PathBuf = arg.into();
-                        match path.extension() {
-                            Some(s) => {
-                                match s.to_str() {
-                                    // leave the file alone, it already has
-                                    // a valid extension
-                                    Some(CSV_EXT) | Some(CUSTOM_EXT) => {}
-                                    _ => {
-                                        path.add_extension(CUSTOM_EXT);
-                                    }
-                                }
-                            }
-                            None => {
-                                path.add_extension(CUSTOM_EXT);
-                            }
-                        };
+                        let path: PathBuf = arg.into();
 
-                        // TODO Check if the file exists, but the program wasn't opened with it. We might be accidentally overwriting something else.
-                        // let mut file = fs::OpenOptions::new().write(true).append(false).truncate(true).create(true).open(path)?;
+                        // TODO Check if the file we are writing to exists, since
+                        // this code path already knows that we are writing to a new file.
+                        // We might be accidentally overwriting something else.
 
                         if let Err(e) = app.grid.save_to(&path) {
                             app.msg = StatusMessage::error(format!("{e}"));