diff --git a/FirebaseUI/Auth/AuthUI/Source/FIRAuthProviderUI.h b/FirebaseUI/Auth/AuthUI/Source/FIRAuthProviderUI.h
index 7a2e287b909..308ed3fdee2 100644
--- a/FirebaseUI/Auth/AuthUI/Source/FIRAuthProviderUI.h
+++ b/FirebaseUI/Auth/AuthUI/Source/FIRAuthProviderUI.h
@@ -99,7 +99,7 @@ typedef void (^FIRAuthProviderSignInCompletionBlock)(FIRAuthCredential *_Nullabl
     @param sourceApplication The application which tried opening the URL.
     @return YES if your auth provider handled the URL. NO otherwise.
  */
-- (BOOL)handleOpenURL:(NSURL *)URL sourceApplication:(NSString *)sourceApplication;
+- (BOOL)handleOpenURL:(NSURL *)URL sourceApplication:(nullable NSString *)sourceApplication;
 
 @end
 
diff --git a/FirebaseUI/Auth/AuthUI/Source/FIRAuthUI.h b/FirebaseUI/Auth/AuthUI/Source/FIRAuthUI.h
index 8631eb96369..52d5660ddca 100644
--- a/FirebaseUI/Auth/AuthUI/Source/FIRAuthUI.h
+++ b/FirebaseUI/Auth/AuthUI/Source/FIRAuthUI.h
@@ -44,9 +44,7 @@ typedef void (^FIRAuthUIResultCallback)(FIRUser *_Nullable user, NSError *_Nulla
     @param user The signed in user if the sign in attempt was successful.
     @param error The error that occured during sign in, if any.
  */
-- (void)authUI:(FIRAuthUI *)authUI
-      didSignInWithUser:(nullable FIRUser *)user
-                  error:(nullable NSError *)error;
+- (void)authUI:(FIRAuthUI *)authUI didSignInWithUser:(nullable FIRUser *)user error:(nullable NSError *)error;
 
 @optional
 
@@ -126,7 +124,7 @@ typedef void (^FIRAuthUIResultCallback)(FIRUser *_Nullable user, NSError *_Nulla
     @return YES if Firebase Auth UI handled the URL. NO otherwise.
  */
 - (BOOL)handleOpenURL:(NSURL *)URL
-    sourceApplication:(NSString *)sourceApplication;
+    sourceApplication:(nullable NSString *)sourceApplication;
 
 /** @fn authViewController
     @brief Returns an instance of the initial view controller of AuthUI.