diff --git a/src/get_save_type.ts b/src/get_save_type.ts
index 25edefbf1b..8585ba1bcc 100644
--- a/src/get_save_type.ts
+++ b/src/get_save_type.ts
@@ -5,4 +5,5 @@ export default function getSaveType (opts: PublicInstallationOptions): Dependenc
   if (opts.save || opts.global) return 'dependencies'
   if (opts.saveDev) return 'devDependencies'
   if (opts.saveOptional) return 'optionalDependencies'
+  return null
 }
diff --git a/src/install/link_bins.ts b/src/install/link_bins.ts
index d4199000f5..e4aab47f6d 100644
--- a/src/install/link_bins.ts
+++ b/src/install/link_bins.ts
@@ -55,7 +55,7 @@ function isScopedPkgsDir (dirPath: string) {
 export function linkPkgBins (modules: string, target: string) {
   const pkg = tryRequire(path.join(target, 'package.json'))
 
-  if (!pkg || !pkg.bin) return
+  if (!pkg || !pkg.bin) return Promise.resolve()
 
   const bins = binify(pkg)
   const binDir = path.join(modules, '.bin')
@@ -140,5 +140,5 @@ function cmdShim (proxyPath: string, targetPath: string) {
  */
 
 function tryRequire (path: string) {
-  try { return requireJson(path) } catch (e) { }
+  try { return requireJson(path) } catch (e) { return null }
 }
diff --git a/src/install/link_peers.ts b/src/install/link_peers.ts
index 50c290893b..4f52d3a4eb 100644
--- a/src/install/link_peers.ts
+++ b/src/install/link_peers.ts
@@ -10,7 +10,7 @@ import {InstalledPackages} from '../api/install'
  */
 
 export default function linkPeers (store: string, installs: InstalledPackages) {
-  if (!installs) return
+  if (!installs) return Promise.resolve()
   const peers = {}
   const roots = {}
 
diff --git a/tsconfig.json b/tsconfig.json
index 606587d602..d509dfdf2e 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -5,7 +5,7 @@
     "sourceMap": true,
     "declaration": true,
     "noImplicitAny": true,
-    "noImplicitReturns": false,
+    "noImplicitReturns": true,
     "suppressImplicitAnyIndexErrors": true,
     "target": "es6",
     "outDir": "lib",