diff --git a/src/posix/cocoa/i_common.h b/src/posix/cocoa/i_common.h
index dc6bea2abe..09281713f3 100644
--- a/src/posix/cocoa/i_common.h
+++ b/src/posix/cocoa/i_common.h
@@ -31,7 +31,10 @@
  **
  */
 
-#include <AppKit/NSApplication.h>
+#import <AppKit/NSApplication.h>
+#import <AppKit/NSScreen.h>
+#import <AppKit/NSView.h>
+#import <AppKit/NSWindow.h>
 
 
 inline bool I_IsHiDPISupported()
diff --git a/src/posix/cocoa/i_input.mm b/src/posix/cocoa/i_input.mm
index 3abea1cb2b..ad2a3d1bd7 100644
--- a/src/posix/cocoa/i_input.mm
+++ b/src/posix/cocoa/i_input.mm
@@ -31,8 +31,12 @@
  **
  */
 
-#include <AppKit/AppKit.h>
-#include <Carbon/Carbon.h>
+#import <AppKit/NSCursor.h>
+#import <AppKit/NSEvent.h>
+#import <Carbon/Carbon.h>
+
+// Avoid collision between DObject class and Objective-C
+#define Class ObjectClass
 
 #include "c_console.h"
 #include "c_cvars.h"
@@ -47,6 +51,8 @@
 #include "i_common.h"
 #include "i_rbopts.h"
 
+#undef Class
+
 
 EXTERN_CVAR(Int, m_use_mouse)
 
diff --git a/src/posix/cocoa/i_main.mm b/src/posix/cocoa/i_main.mm
index 8277e587b6..f7f7321240 100644
--- a/src/posix/cocoa/i_main.mm
+++ b/src/posix/cocoa/i_main.mm
@@ -33,8 +33,11 @@
 
 #include <sys/sysctl.h>
 
-#include <AppKit/NSMenu.h>
-#include <AppKit/NSScreen.h>
+#import <AppKit/NSMenu.h>
+#import <AppKit/NSEvent.h>
+
+// Avoid collision between DObject class and Objective-C
+#define Class ObjectClass
 
 #include "c_console.h"
 #include "c_cvars.h"
@@ -50,6 +53,8 @@
 #include "i_osversion.h"
 #include "i_rbopts.h"
 
+#undef Class
+
 
 #define ZD_UNUSED(VARIABLE) ((void)(VARIABLE))
 
diff --git a/src/posix/cocoa/i_video.mm b/src/posix/cocoa/i_video.mm
index 61e1602252..0a872e88eb 100644
--- a/src/posix/cocoa/i_video.mm
+++ b/src/posix/cocoa/i_video.mm
@@ -31,16 +31,17 @@
  **
  */
 
-#include <AppKit/NSBitmapImageRep.h>
-#include <AppKit/NSButton.h>
-#include <AppKit/NSCursor.h>
-#include <AppKit/NSImage.h>
-#include <AppKit/NSOpenGL.h>
-#include <AppKit/NSOpenGLView.h>
-#include <AppKit/NSWindow.h>
-#include <Carbon/Carbon.h>
-#include <OpenGL/gl.h>
-#include <OpenGL/OpenGL.h>
+#import <AppKit/NSButton.h>
+#import <AppKit/NSCursor.h>
+#import <AppKit/NSImage.h>
+#import <AppKit/NSOpenGL.h>
+#import <AppKit/NSOpenGLView.h>
+#import <Carbon/Carbon.h>
+#import <OpenGL/gl.h>
+#import <OpenGL/OpenGL.h>
+
+// Avoid collision between DObject class and Objective-C
+#define Class ObjectClass
 
 #include "bitmap.h"
 #include "c_dispatch.h"
@@ -61,6 +62,8 @@
 #include "i_common.h"
 #include "i_rbopts.h"
 
+#undef Class
+
 
 EXTERN_CVAR(Bool, ticker   )
 EXTERN_CVAR(Bool, vid_vsync)
@@ -215,7 +218,7 @@ public:
 	virtual void SetVSync(bool vsync);
 
 private:
-	const size_t BYTES_PER_PIXEL = 4;
+	static const size_t BYTES_PER_PIXEL = 4;
 
 	PalEntry m_palette[256];
 	bool     m_needPaletteUpdate;