diff --git a/src/classes/Auth/Auth.ts b/src/classes/Auth/Auth.ts
index 213b01a..649882e 100644
--- a/src/classes/Auth/Auth.ts
+++ b/src/classes/Auth/Auth.ts
@@ -26,6 +26,14 @@ export class Auth extends PassageBase {
      * @return {Promise<string>} The transaction ID
      */
     public async createRegisterTransaction(externalId: string, passkeyDisplayName: string): Promise<string> {
+        if (!externalId) {
+            throw new Error('externalId is required.');
+        }
+
+        if (!passkeyDisplayName) {
+            throw new Error('passkeyDisplayName is required.');
+        }
+
         try {
             const response = await this.transactionClient.createRegisterTransaction({
                 appId: this.config.appId,
@@ -48,6 +56,10 @@ export class Auth extends PassageBase {
      * @return {Promise<string>} The transaction ID
      */
     public async createAuthenticateTransaction(externalId: string): Promise<string> {
+        if (!externalId) {
+            throw new Error('externalId is required.');
+        }
+
         try {
             const response = await this.transactionClient.createAuthenticateTransaction({
                 appId: this.config.appId,
@@ -67,6 +79,10 @@ export class Auth extends PassageBase {
      * @return {Promise<string>} The unique identifier of the user associated with the nonce
      */
     public async verifyNonce(nonce: string): Promise<string> {
+        if (!nonce) {
+            throw new Error('nonce is required.');
+        }
+
         try {
             const response = await this.authClient.authenticateVerifyNonce({
                 appId: this.config.appId,
diff --git a/src/classes/PassageFlex/PassageFlex.spec.ts b/src/classes/PassageFlex/PassageFlex.spec.ts
index 0de71e3..0a6e9d3 100644
--- a/src/classes/PassageFlex/PassageFlex.spec.ts
+++ b/src/classes/PassageFlex/PassageFlex.spec.ts
@@ -24,7 +24,7 @@ describe('PassageFlex', () => {
             } as unknown as PassageFlexConfig;
 
             expect(() => new PassageFlex(config)).toThrow(
-                'A Passage app ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.',
+                'A Passage App ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.',
             );
         });
 
@@ -35,7 +35,7 @@ describe('PassageFlex', () => {
             };
 
             expect(() => new PassageFlex(config)).toThrow(
-                'A Passage app ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.',
+                'A Passage App ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.',
             );
         });
 
diff --git a/src/classes/PassageFlex/PassageFlex.ts b/src/classes/PassageFlex/PassageFlex.ts
index 58605ac..2958d12 100644
--- a/src/classes/PassageFlex/PassageFlex.ts
+++ b/src/classes/PassageFlex/PassageFlex.ts
@@ -17,7 +17,7 @@ export class PassageFlex {
      */
     public constructor(config: PassageFlexConfig) {
         if (!config.appId) {
-            throw Error('A Passage app ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.');
+            throw Error('A Passage App ID is required. Please include {appId: YOUR_APP_ID, apiKey: YOUR_APP_ID}.');
         }
 
         if (!config.apiKey) {
diff --git a/src/classes/User/User.ts b/src/classes/User/User.ts
index 15be584..4c594af 100644
--- a/src/classes/User/User.ts
+++ b/src/classes/User/User.ts
@@ -82,6 +82,14 @@ export class User extends PassageBase {
      * @return {Promise<void>}
      */
     public async revokeDevice(externalId: string, deviceId: string): Promise<void> {
+        if (!externalId) {
+            throw new Error('externalId is required.');
+        }
+
+        if (!deviceId) {
+            throw new Error('deviceId is required.');
+        }
+
         try {
             const user = await this.get(externalId);
             await this.deviceClient.deleteUserDevices({