diff --git a/lib/googleauth/user_authorizer.rb b/lib/googleauth/user_authorizer.rb
index e6948d5..ccd24d9 100644
--- a/lib/googleauth/user_authorizer.rb
+++ b/lib/googleauth/user_authorizer.rb
@@ -55,21 +55,25 @@ class UserAuthorizer
       #  Authorization scope to request
       # @param [Google::Auth::Stores::TokenStore] token_store
       #  Backing storage for persisting user credentials
-      # @param [String] callback_uri
+      # @param [String] legacy_callback_uri
       #  URL (either absolute or relative) of the auth callback.
-      #  Defaults to '/oauth2callback'
+      #  Defaults to '/oauth2callback'.
+      #  @deprecated This field is deprecated. Instead, use the keyword
+      #   argument callback_uri.
       # @param [String] code_verifier
       #  Random string of 43-128 chars used to verify the key exchange using
       #  PKCE.
       def initialize client_id, scope, token_store,
-                     callback_uri = nil, code_verifier: nil
+                     legacy_callback_uri = nil,
+                     callback_uri: nil,
+                     code_verifier: nil
         raise NIL_CLIENT_ID_ERROR if client_id.nil?
         raise NIL_SCOPE_ERROR if scope.nil?
 
         @client_id = client_id
         @scope = Array(scope)
         @token_store = token_store
-        @callback_uri = callback_uri || "/oauth2callback"
+        @callback_uri = legacy_callback_uri || callback_uri || "/oauth2callback"
         @code_verifier = code_verifier
       end
 
diff --git a/lib/googleauth/web_user_authorizer.rb b/lib/googleauth/web_user_authorizer.rb
index ddf9644..75183c3 100644
--- a/lib/googleauth/web_user_authorizer.rb
+++ b/lib/googleauth/web_user_authorizer.rb
@@ -93,15 +93,22 @@ def self.handle_auth_callback_deferred request
       #  Authorization scope to request
       # @param [Google::Auth::Stores::TokenStore] token_store
       #  Backing storage for persisting user credentials
-      # @param [String] callback_uri
+      # @param [String] legacy_callback_uri
       #  URL (either absolute or relative) of the auth callback. Defaults
-      #  to '/oauth2callback'
+      #  to '/oauth2callback'.
+      #  @deprecated This field is deprecated. Instead, use the keyword
+      #   argument callback_uri.
       # @param [String] code_verifier
       #  Random string of 43-128 chars used to verify the key exchange using
       #  PKCE.
       def initialize client_id, scope, token_store,
-                     callback_uri = nil, code_verifier: nil
-        super client_id, scope, token_store, callback_uri, code_verifier: code_verifier
+                     legacy_callback_uri = nil,
+                     callback_uri: nil,
+                     code_verifier: nil
+        super client_id, scope, token_store,
+              legacy_callback_uri,
+              code_verifier: code_verifier,
+              callback_uri: callback_uri
       end
 
       # Handle the result of the oauth callback. Exchanges the authorization
diff --git a/spec/googleauth/user_authorizer_spec.rb b/spec/googleauth/user_authorizer_spec.rb
index 2a176ae..9fb3157 100644
--- a/spec/googleauth/user_authorizer_spec.rb
+++ b/spec/googleauth/user_authorizer_spec.rb
@@ -85,7 +85,7 @@
       Google::Auth::UserAuthorizer.new(client_id,
                                        scope,
                                        token_store,
-                                       callback_uri)
+                                       callback_uri: callback_uri)
     end
     let :uri do
       authorizer.get_authorization_url login_hint: "user1", state: "mystate"