diff --git a/package.json b/package.json
index 1d0bbf61..10607edf 100644
--- a/package.json
+++ b/package.json
@@ -4,6 +4,7 @@
   "author": "Steven Hugg",
   "dependencies": {},
   "devDependencies": {
+    "typescript": "^2.9.2",
     "@types/jquery": "^3.3.4",
     "mocha": "^3.2.0",
     "mocha-phantomjs": "^4.1.0",
diff --git a/src/ui.js b/src/ui.js
index 34822c9d..8eeadf73 100644
--- a/src/ui.js
+++ b/src/ui.js
@@ -501,12 +501,6 @@ function clearBreakpoint() {
   showMemory();
 }
 
-function jumpToLine(ed, i) {
-  var t = ed.charCoords({line: i, ch: 0}, "local").top;
-  var middleHeight = ed.getScrollerElement().offsetHeight / 2;
-  ed.scrollTo(null, t - middleHeight - 5);
-}
-
 function resetAndDebug() {
   if (platform.setupDebug && platform.readAddress) { // TODO??
     clearBreakpoint();
diff --git a/src/views.ts b/src/views.ts
index 0226dece..cf819ab8 100644
--- a/src/views.ts
+++ b/src/views.ts
@@ -13,7 +13,12 @@ var pixeditframe;
 
 // TODO: functions
 var inspectVariable;
-var jumpToLine;
+
+function jumpToLine(ed, i:number) {
+  var t = ed.charCoords({line: i, ch: 0}, "local").top;
+  var middleHeight = ed.getScrollerElement().offsetHeight / 2;
+  ed.scrollTo(null, t - middleHeight - 5);
+}
 
 // TODO: remove some calls of global functions
 function SourceEditor(path, mode) {