diff --git a/src/server/auth/errors.ts b/src/server/auth/errors.ts
index e6871a19b..dff413e38 100644
--- a/src/server/auth/errors.ts
+++ b/src/server/auth/errors.ts
@@ -163,6 +163,14 @@ export class InsufficientScopeError extends OAuthError {
     static errorCode = 'insufficient_scope';
 }
 
+/**
+ * Invalid target error - The requested resource is invalid, missing, unknown, or malformed.
+ * (Custom error for resource indicators - RFC 8707)
+ */
+export class InvalidTargetError extends OAuthError {
+    static errorCode = 'invalid_target';
+}
+
 /**
  * A utility class for defining one-off error codes
  */
@@ -199,5 +207,6 @@ export const OAUTH_ERRORS = {
     [MethodNotAllowedError.errorCode]: MethodNotAllowedError,
     [TooManyRequestsError.errorCode]: TooManyRequestsError,
     [InvalidClientMetadataError.errorCode]: InvalidClientMetadataError,
-    [InsufficientScopeError.errorCode]: InsufficientScopeError
+    [InsufficientScopeError.errorCode]: InsufficientScopeError,
+    [InvalidTargetError.errorCode]: InvalidTargetError
 } as const;