Keep the class forward declaration also.
Some users might be depended on these, so until everything is flipped to
explicit imports, need to still provide the class declaration so the proto isn't
a breaking change.
diff --git a/objectivec/GPBCodedInputStream.h b/objectivec/GPBCodedInputStream.h
index 73b6558..2b95cc9 100644
--- a/objectivec/GPBCodedInputStream.h
+++ b/objectivec/GPBCodedInputStream.h
@@ -31,6 +31,7 @@
#import <Foundation/Foundation.h>
@class GPBMessage;
+@class GPBExtensionRegistry;
@protocol GPBExtensionRegistry;
NS_ASSUME_NONNULL_BEGIN
diff --git a/objectivec/GPBMessage.h b/objectivec/GPBMessage.h
index 990a796..ddd5de7 100644
--- a/objectivec/GPBMessage.h
+++ b/objectivec/GPBMessage.h
@@ -36,6 +36,7 @@
@class GPBCodedInputStream;
@class GPBCodedOutputStream;
@class GPBExtensionDescriptor;
+@class GPBExtensionRegistry;
@protocol GPBExtensionRegistry;
@class GPBFieldDescriptor;
@class GPBUnknownFieldSet;
