diff --git a/src/resolve.ts b/src/resolve.ts
index 011295f..593d58a 100644
--- a/src/resolve.ts
+++ b/src/resolve.ts
@@ -124,19 +124,22 @@ function _resolve(id: string, options: ResolveOptions = {}): string {
   return pathToFileURL(realPath).toString();
 }
 
-export function resolveSync(id: string, options?: ResolveOptions) {
+export function resolveSync(id: string, options?: ResolveOptions): string {
   return _resolve(id, options);
 }
 
-export function resolve(id: string, options?: ResolveOptions) {
+export function resolve(id: string, options?: ResolveOptions): Promise<string> {
   return pcall(resolveSync, id, options);
 }
 
-export function resolvePathSync(id: string, options?: ResolveOptions) {
+export function resolvePathSync(id: string, options?: ResolveOptions): string {
   return fileURLToPath(resolveSync(id, options));
 }
 
-export function resolvePath(id: string, options?: ResolveOptions) {
+export function resolvePath(
+  id: string,
+  options?: ResolveOptions
+): Promise<string> {
   return pcall(resolvePathSync, id, options);
 }