diff --git a/npm/bin/lsif-npm b/npm/bin/lsif-npm
old mode 100644
new mode 100755
index c6524eba..7e307f19
--- a/npm/bin/lsif-npm
+++ b/npm/bin/lsif-npm
@@ -1,2 +1,2 @@
-#!/usr/bin/env node
+#!/usr/bin/env node
 require('../lib/main.js').main();
\ No newline at end of file
diff --git a/npm/src/main.ts b/npm/src/main.ts
index 7ee5c698..078deb9a 100644
--- a/npm/src/main.ts
+++ b/npm/src/main.ts
@@ -86,11 +86,23 @@ function makeAbsolute(p: string, root?: string): string {
 	}
 }
 
+const makeIntIdGenerator = () => {
+	let counter = Number.MAX_SAFE_INTEGER;
+
+	return () => {
+		return counter--;
+	}
+}
+
+const uuidIdGenerator = () => {
+	return uuid.v4()
+}
+
 class Linker {
 
 	private _idGenerator: (() => Id) | undefined;
 
-	constructor() {
+	constructor(private intIdGenerator: () => Id) {
 	}
 
 	protected get idGenerator(): () => Id {
@@ -105,14 +117,9 @@ class Linker {
 			return;
 		}
 		if (typeof id === 'number') {
-			let counter = Number.MAX_SAFE_INTEGER;
-			this._idGenerator = () => {
-				return counter--;
-			};
+			this._idGenerator = this.intIdGenerator
 		} else {
-			this._idGenerator = () => {
-				return uuid.v4();
-			};
+			this._idGenerator = uuidIdGenerator
 		}
 	}
 
@@ -167,8 +174,8 @@ class ExportLinker extends Linker {
 
 	private packageInformation: PackageInformation | undefined;
 
-	constructor(private projectRoot: string, private packageJson: PackageJson) {
-		super();
+	constructor(private projectRoot: string, private packageJson: PackageJson, intIdGenerator: () => Id) {
+		super(intIdGenerator);
 	}
 
 	public handleMoniker(moniker: Moniker): void {
@@ -212,8 +219,8 @@ class ImportLinker extends Linker {
 
 	private packageData: Map<string,  { packageInfo: PackageInformation, packageJson: PackageJson } | null>;
 
-	constructor(private projectRoot: string) {
-		super();
+	constructor(private projectRoot: string, intIdGenerator: () => Id) {
+		super(intIdGenerator);
 		this.packageData = new Map();
 	}
 
@@ -354,11 +361,12 @@ export function main(): void {
 		return;
 	}
 
+	const intIdGenerator = makeIntIdGenerator()
 	let exportLinker: ExportLinker | undefined;
 	if (packageJson !== undefined) {
-		exportLinker = new ExportLinker(projectRoot, packageJson);
+		exportLinker = new ExportLinker(projectRoot, packageJson, intIdGenerator);
 	}
-	const importLinker: ImportLinker = new ImportLinker(projectRoot);
+	const importLinker: ImportLinker = new ImportLinker(projectRoot, intIdGenerator);
 	let input: NodeJS.ReadStream | fs.ReadStream = process.stdin;
 	if (options.in !== undefined && fs.existsSync(options.in)) {
 		input = fs.createReadStream(options.in, { encoding: 'utf8'});