diff --git a/src/esm.ts b/src/esm.ts
index 2e221ad..4199e54 100644
--- a/src/esm.ts
+++ b/src/esm.ts
@@ -8,7 +8,7 @@ export type ESMImport = string | { name: string; as?: string };
 export function genImport(
   specifier: string,
   imports?: ESMImport | ESMImport[],
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) {
   return _genStatement("import", specifier, imports, options);
 }
@@ -16,7 +16,7 @@ export function genImport(
 export function genTypeImport(
   specifier: string,
   imports: ESMImport[],
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) {
   return _genStatement("import type", specifier, imports, options);
 }
@@ -24,7 +24,7 @@ export function genTypeImport(
 export function genTypeExport(
   specifier: string,
   imports: ESMImport[],
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) {
   return _genStatement("export type", specifier, imports, options);
 }
@@ -32,7 +32,7 @@ export function genTypeExport(
 export const genInlineTypeImport = (
   specifier: string,
   name = "default",
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) => {
   return `typeof ${genDynamicImport(specifier, {
     ...options,
@@ -47,7 +47,7 @@ export type ESMExport = string | { name: string; as?: string };
 export function genExport(
   specifier: string,
   exports?: ESMExport | ESMExport[],
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) {
   return _genStatement("export", specifier, exports, options);
 }
@@ -58,7 +58,7 @@ function _genStatement(
   type: ImportExportType,
   specifier: string,
   names?: ESMImportOrExport | ESMImportOrExport[],
-  options: CodegenOptions = {}
+  options: CodegenOptions = {},
 ) {
   const specifierString = genString(specifier, options);
   if (!names) {
@@ -85,12 +85,12 @@ function _genStatement(
   if (nameArray) {
     return `${type} { ${namesString} } from ${genString(
       specifier,
-      options
+      options,
     )}${_genAssertClause(type, options.assert)};`;
   }
   return `${type} ${namesString} from ${genString(
     specifier,
-    options
+    options,
   )}${_genAssertClause(type, options.assert)};`;
 }
 
@@ -118,7 +118,7 @@ export interface DynamicImportOptions extends CodegenOptions {
 }
 export function genDynamicImport(
   specifier: string,
-  options: DynamicImportOptions = {}
+  options: DynamicImportOptions = {},
 ) {
   const commentString = options.comment ? ` /* ${options.comment} */` : "";
   const wrapperString = options.wrapper === false ? "" : "() => ";
@@ -128,7 +128,7 @@ export function genDynamicImport(
   const optionsString = _genDynamicImportOptions(options);
   return `${wrapperString}import(${genString(
     specifier,
-    options
+    options,
   )}${commentString}${optionsString})${ineropString}`;
 }
 
diff --git a/src/object.ts b/src/object.ts
index 59e5e48..6ef5163 100644
--- a/src/object.ts
+++ b/src/object.ts
@@ -2,7 +2,7 @@ import { genObjectKey, wrapInDelimiters } from "./utils";
 
 export function genObjectFromRaw(
   object: Record<string, any>,
-  indent = ""
+  indent = "",
 ): string {
   return genObjectFromRawEntries(Object.entries(object), indent);
 }
@@ -12,29 +12,29 @@ export function genArrayFromRaw(array: any[], indent = "") {
   return wrapInDelimiters(
     array.map((index) => `${newIdent}${genRawValue(index, newIdent)}`),
     indent,
-    "[]"
+    "[]",
   );
 }
 
 export function genObjectFromRawEntries(
   array: [key: string, value: any][],
-  indent = ""
+  indent = "",
 ) {
   const newIdent = indent + "  ";
   return wrapInDelimiters(
     array.map(
       ([key, value]) =>
-        `${newIdent}${genObjectKey(key)}: ${genRawValue(value, newIdent)}`
+        `${newIdent}${genObjectKey(key)}: ${genRawValue(value, newIdent)}`,
     ),
     indent,
-    "{}"
+    "{}",
   );
 }
 
 // --- Internals ---
 
 function genRawValue(value: unknown, indent = ""): string {
-  if (typeof value === "undefined" || value === undefined) {
+  if (value === undefined) {
     return "undefined";
   }
   if (value === null) {
diff --git a/src/typescript.ts b/src/typescript.ts
index 5b1993e..ce4f1e7 100644
--- a/src/typescript.ts
+++ b/src/typescript.ts
@@ -20,19 +20,19 @@ export const genTypeObject = (object: TypeObject, indent = ""): string => {
       }
       return `${newIndent}${genObjectKey(k)}${optional}: ${genTypeObject(
         value,
-        newIndent
+        newIndent,
       )}`;
     }),
     indent,
     "{}",
-    false
+    false,
   );
 };
 
 export const genInterface = (
   name: string,
   contents?: TypeObject,
-  options: GenInterfaceOptions = {}
+  options: GenInterfaceOptions = {},
 ) => {
   const result = [
     options.export && "export",
@@ -55,7 +55,7 @@ export const genAugmentation = (
   interfaces?: Record<
     string,
     TypeObject | [TypeObject, Omit<GenInterfaceOptions, "export">]
-  >
+  >,
 ) => {
   return `declare module ${genString(specifier)} ${wrapInDelimiters(
     Object.entries(interfaces || {}).map(
@@ -63,7 +63,7 @@ export const genAugmentation = (
         "  " +
         (Array.isArray(entry)
           ? genInterface(key, ...entry)
-          : genInterface(key, entry))
-    )
+          : genInterface(key, entry)),
+    ),
   )}`;
 };
diff --git a/src/utils.ts b/src/utils.ts
index 5f63cd7..1e513d1 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -4,7 +4,7 @@ export function wrapInDelimiters(
   lines: string[],
   indent = "",
   delimiters = "{}",
-  withComma = true
+  withComma = true,
 ) {
   if (lines.length === 0) {
     return delimiters;