diff --git a/src/NativeReactNativeBiometrics.ts b/src/NativeReactNativeBiometrics.ts
index 80f6178..1a205b5 100644
--- a/src/NativeReactNativeBiometrics.ts
+++ b/src/NativeReactNativeBiometrics.ts
@@ -84,7 +84,7 @@ export interface Spec extends TurboModule {
     error?: string;
   }>;
   verifyKeySignature(
-    keyAlias: string,
+    keyAlias: string | null,
     data: string,
     promptTitle?: string,
     promptSubtitle?: string,
diff --git a/src/index.tsx b/src/index.tsx
index 1a8d4e9..74dc88a 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -269,12 +269,13 @@ export function verifyKeySignature(
   cancelButtonText?: string,
   returnAuthType?: boolean
 ): Promise<SignatureResult> {
+  const resolvedKeyAlias = keyAlias || null;
   logger.debug('Verifying key signature', 'verifyKeySignature', {
     keyAlias,
     dataLength: data.length,
   });
   return ReactNativeBiometrics.verifyKeySignature(
-    keyAlias,
+    resolvedKeyAlias,
     data,
     promptTitle,
     promptSubtitle,
@@ -341,6 +342,8 @@ export function signWithOptions(
     returnAuthType,
   } = options;
 
+  const resolvedKeyAlias = keyAlias || null;
+
   logger.debug('Signing with options', 'signWithOptions', {
     keyAlias,
     dataLength: data.length,
@@ -361,7 +364,7 @@ export function signWithOptions(
   // On Android, use the new method with options
   if (Platform.OS === 'android') {
     return ReactNativeBiometrics.verifyKeySignatureWithOptions(
-      keyAlias,
+      resolvedKeyAlias,
       data,
       promptTitle,
       promptSubtitle,
@@ -388,7 +391,7 @@ export function signWithOptions(
 
   // On iOS, use the standard method with inputEncoding
   return ReactNativeBiometrics.verifyKeySignatureWithEncoding(
-    keyAlias,
+    resolvedKeyAlias,
     data,
     promptTitle,
     promptSubtitle,