diff --git a/Source/NSPersistentDocument.m b/Source/NSPersistentDocument.m
index 36b769c0a..603f8ff6d 100644
--- a/Source/NSPersistentDocument.m
+++ b/Source/NSPersistentDocument.m
@@ -22,6 +22,11 @@
    Boston, MA 02110 USA.
 */
 
+#import <Foundation/NSURL.h>
+#import <Foundation/NSString.h>
+#import <Foundation/NSDictionary.h>
+#import <Foundation/NSError.h>
+#import <Foundation/NSUndoManager.h>
 #import "AppKit/NSPersistentDocument.h"
 
 @implementation NSPersistentDocument