diff --git a/Focus.omnijs b/Focus.ts
similarity index 68%
rename from Focus.omnijs
rename to Focus.ts
index 67dd857..c0106e4 100644
--- a/Focus.omnijs
+++ b/Focus.ts
@@ -4,14 +4,14 @@
   "author": "Brian Hicks",
   "identifier": "zone.bytes.focus",
   "version": "1.0",
-  "description": "Start and log a pomodoro for the selected task",
+  "description": "Start a pomodoro for the selected task",
   "label": "Focus",
   "shortLabel": "Focus",
   "paletteLabel": "Focus",
   "image": "clock"
 }*/
 (() => {
-  var action = new PlugIn.Action(async (selection, sender) => {
+  var action = new PlugIn.Action(async (selection: Selection, sender: any) => {
     try {
       let task = selection.tasks[0]
 
@@ -39,16 +39,26 @@
       focusForm.addField(new Form.Field.String("project", "Project", task.containingProject ? task.containingProject.name : null));
       focusForm.addField(new Form.Field.Option("category", "Category", possibleCategories, possibleCategories, defaultCategory));
       focusForm.addField(new Form.Field.String("minutes", "Minutes", "25"));
+
       await focusForm.show("Focus on…", "Start");
+      let values = focusForm.values as {
+          project: string,
+          category: string,
+          minutes: string,
+      };
 
-      let sessionUrl = URL.fromString(`session:///start?intent=${encodeURIComponent(focusForm.values.project)}&categoryName=${encodeURIComponent(focusForm.values.category)}&duration=${encodeURIComponent(focusForm.values.minutes)}`)
+      let rawSessionUrl = `session:///start?intent=${encodeURIComponent(values.project)}&categoryName=${encodeURIComponent(values.category)}&duration=${encodeURIComponent(values.minutes)}`
+      let sessionUrl = URL.fromString(rawSessionUrl)
+      if (sessionUrl === null) {
+          throw `failed to parse session string ("${rawSessionUrl}") into a URL`
+      }
       sessionUrl.open();
     } catch (err) {
       console.error(err);
     }
   });
 
-  action.validate = function(selection, sender){
+  action.validate = function(selection: Selection, sender: any){
     return (selection.tasks.length === 1)
   };