diff --git a/packages/react-native/ReactCommon/react/bridgeless/platform/ios/Core/RCTInstance.h b/packages/react-native/ReactCommon/react/bridgeless/platform/ios/Core/RCTInstance.h
index 5751cb5cc59..ed49c7938df 100644
--- a/packages/react-native/ReactCommon/react/bridgeless/platform/ios/Core/RCTInstance.h
+++ b/packages/react-native/ReactCommon/react/bridgeless/platform/ios/Core/RCTInstance.h
@@ -14,15 +14,15 @@
 #import <react/renderer/mapbuffer/MapBuffer.h>
 #import <react/utils/ContextContainer.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  * A utility to enable diagnostics mode at runtime. Useful for test runs.
  * The flags are comma-separated string tokens, or an empty string when
  * nothing is enabled.
  */
 RCT_EXTERN NSString *RCTInstanceRuntimeDiagnosticFlags(void);
-RCT_EXTERN void RCTInstanceSetRuntimeDiagnosticFlags(NSString *flags);
-
-NS_ASSUME_NONNULL_BEGIN
+RCT_EXTERN void RCTInstanceSetRuntimeDiagnosticFlags(NSString *_Nullable flags);
 
 @class RCTBundleManager;
 @class RCTInstance;