diff --git a/extension/ui/src/Visualizers/AstViewer.tsx b/extension/ui/src/Visualizers/AstViewer.tsx
index bce37b9..99329ce 100644
--- a/extension/ui/src/Visualizers/AstViewer.tsx
+++ b/extension/ui/src/Visualizers/AstViewer.tsx
@@ -35,10 +35,7 @@ export class AstVisualizer extends VisualizationProvider {
 					const m = createTreeViewModelFromTreeNodeData(data.root);
 					const l = LineColumn(data.text);
 					function translatePosition(pos: number): monaco.IPosition {
-						const r = l.fromIndex(pos) as {
-							line: number;
-							col: number;
-						};
+						const r = l.fromIndex(pos);
 						return {
 							column: r.col,
 							lineNumber: r.line,
diff --git a/extension/ui/src/Visualizers/types.d.ts b/extension/ui/src/Visualizers/types.d.ts
index 15425d7..2320986 100644
--- a/extension/ui/src/Visualizers/types.d.ts
+++ b/extension/ui/src/Visualizers/types.d.ts
@@ -7,3 +7,16 @@ declare module "viz.js/full.render.js" {
 	export const render: any;
 	export const Module: any;
 }
+
+declare module "line-column" {
+	export = function(
+		text: string
+	): {
+		fromIndex(
+			idx: number
+		): {
+			line: number;
+			col: number;
+		};
+	} {};
+}