diff --git a/Source/exehead/Ui.c b/Source/exehead/Ui.c
index 117ac9ad..c8a1855f 100644
--- a/Source/exehead/Ui.c
+++ b/Source/exehead/Ui.c
@@ -31,6 +31,7 @@
 #include "plugin.h"
 #include "lang.h"
 #include "components.h"
+#include "api.h"
 
 #ifdef NSIS_CONFIG_VISIBLE_SUPPORT
 HICON g_hIcon;
@@ -55,8 +56,6 @@ static char g_tmp[NSIS_MAX_STRLEN * 4];
 static int m_page=-1,m_retcode,m_delta;
 static page *g_this_page;
 
-#define NOTIFY_BYE_BYE 'x'
-
 static void NSISCALL outernotify(int delta) {
   if (delta==NOTIFY_BYE_BYE)
     g_quit_flag++;
diff --git a/Source/exehead/exec.c b/Source/exehead/exec.c
index 60814828..4c066fc0 100644
--- a/Source/exehead/exec.c
+++ b/Source/exehead/exec.c
@@ -26,6 +26,7 @@
 #include "plugin.h"
 #include "lang.h"
 #include "resource.h"
+#include "api.h"
 
 #define EXEC_ERROR 0x7FFFFFFF
 
@@ -45,12 +46,7 @@ static stack_t *g_st;
 exec_flags g_exec_flags;
 exec_flags g_exec_flags_last_used;
 
-struct {
-  exec_flags *flags;
-  void *ExecuteCodeSegment;
-  void *validate_filename;
-  void *RegisterPluginCallback;
-} plugin_extra_parameters = {
+extra_parameters plugin_extra_parameters = {
   &g_exec_flags,
   &ExecuteCodeSegment,
   &validate_filename,
diff --git a/Source/exehead/fileform.h b/Source/exehead/fileform.h
index 3fc55874..2427aa40 100644
--- a/Source/exehead/fileform.h
+++ b/Source/exehead/fileform.h
@@ -16,6 +16,7 @@
 
 #include "config.h"
 #include "../Platform.h"
+#include "api.h"
 
 #ifndef _FILEFORM_H_
 #define _FILEFORM_H_
@@ -484,33 +485,6 @@ typedef struct {
 #define NSIS_INSTDIR_INVALID 1
 #define NSIS_INSTDIR_NOT_ENOUGH_SPACE 2
 
-typedef struct
-{
-  int autoclose;
-  int all_user_var;
-  int exec_error;
-  int abort;
-#ifdef NSIS_SUPPORT_REBOOT
-  int exec_reboot;
-  int reboot_called;
-#else
-  int _;
-  int __;
-#endif
-  int XXX_cur_insttype; // depreacted
-  int plugin_api_version; // used to be XXX_insttype_changed, but that was deprecated
-#ifdef NSIS_CONFIG_SILENT_SUPPORT
-  int silent;
-#else
-  int ___;
-#endif
-  int instdir_error;
-  int rtl;
-  int errlvl;
-  int alter_reg_view;
-  int status_update;
-} exec_flags;
-
 #define FIELDN(x, y) (((int *)&x)[y])
 
 #ifdef EXEHEAD
diff --git a/Source/exehead/plugin.h b/Source/exehead/plugin.h
index 4fe3288f..1e605206 100644
--- a/Source/exehead/plugin.h
+++ b/Source/exehead/plugin.h
@@ -19,28 +19,10 @@
 
 #include "../Platform.h"
 #include "fileform.h"
+#include "api.h"
 
 #ifdef NSIS_CONFIG_PLUGIN_SUPPORT
 
-// Starting with NSIS 2.42, you can check the version of the plugin API in exec_flags->plugin_api_version
-// The format is 0xXXXXYYYY where X is the major version and Y is the minor version (MAKELONG(y,x))
-// When doing version checks, always remember to use >=, ex: if (pX->exec_flags->plugin_api_version >= NSISPIAPIVER_1_0) {}
-
-#define NSISPIAPIVER_1_0 0x00010000
-#define NSISPIAPIVER_CURR NSISPIAPIVER_1_0
-
-// NSIS Plug-In Callback Messages
-enum NSPIM 
-{
-	NSPIM_UNLOAD,    // This is the last message a plugin gets, do final cleanup
-	NSPIM_GUIUNLOAD, // Called after .onGUIEnd
-};
-
-// Prototype for callbacks registered with extra_parameters->RegisterPluginCallback()
-// Return NULL for unknown messages
-// Should always be __cdecl for future expansion possibilities
-typedef UINT_PTR (*NSISPLUGINCALLBACK)(NSPIM);
-
 extern BOOL NSISCALL RegisterPluginCallback(HMODULE pluginHandle, NSISPLUGINCALLBACK proc);
 
 extern void NSISCALL Plugins_SendMsgToAllPlugins(int msg);
diff --git a/Source/exehead/ui.h b/Source/exehead/ui.h
index 8ee0cabc..b9b5fbd4 100644
--- a/Source/exehead/ui.h
+++ b/Source/exehead/ui.h
@@ -36,18 +36,12 @@ void NSISCALL build_g_logfile(void);
 // sent to every child window to tell it it can start executing NSIS code
 #define WM_NOTIFY_START (WM_USER+0x5)
 
-// sent to the outer window to tell it to go to the next inner window
-#define WM_NOTIFY_OUTER_NEXT (WM_USER+0x8)
-
 // sent to every child window to tell it it is closing soon
 #define WM_NOTIFY_INIGO_MONTOYA (WM_USER+0xb)
 
 // update message used by DirProc and SelProc for space display
 #define WM_IN_UPDATEMSG (WM_USER+0xf)
 
-// custom pages should send this message to let NSIS know they're ready
-#define WM_NOTIFY_CUSTOM_READY (WM_USER+0xd)
-
 // simulates clicking on the tree
 #define WM_TREEVIEW_KEYHACK (WM_USER+0x13)