diff --git a/dlls/mciavi32/private_mciavi.h b/dlls/mciavi32/private_mciavi.h
index 548254c5a4f..1ee0eb3432a 100644
--- a/dlls/mciavi32/private_mciavi.h
+++ b/dlls/mciavi32/private_mciavi.h
@@ -82,32 +82,32 @@ typedef struct {
     HANDLE              ack_event; /* acknowledge that an async command has started */
 } WINE_MCIAVI;
 
-extern HINSTANCE MCIAVI_hInstance;
+extern HINSTANCE MCIAVI_hInstance DECLSPEC_HIDDEN;
 
 /* info.c */
-DWORD 	MCIAVI_ConvertTimeFormatToFrame(WINE_MCIAVI* wma, DWORD val);
-DWORD	MCIAVI_mciGetDevCaps(UINT wDevID, DWORD dwFlags,  LPMCI_GETDEVCAPS_PARMS lpParms);
-DWORD	MCIAVI_mciInfo(UINT wDevID, DWORD dwFlags, LPMCI_DGV_INFO_PARMSW lpParms);
-DWORD	MCIAVI_mciSet(UINT wDevID, DWORD dwFlags, LPMCI_DGV_SET_PARMS lpParms);
-DWORD	MCIAVI_mciStatus(UINT wDevID, DWORD dwFlags, LPMCI_DGV_STATUS_PARMSW lpParms);
+DWORD 	MCIAVI_ConvertTimeFormatToFrame(WINE_MCIAVI* wma, DWORD val) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciGetDevCaps(UINT wDevID, DWORD dwFlags,  LPMCI_GETDEVCAPS_PARMS lpParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciInfo(UINT wDevID, DWORD dwFlags, LPMCI_DGV_INFO_PARMSW lpParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciSet(UINT wDevID, DWORD dwFlags, LPMCI_DGV_SET_PARMS lpParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciStatus(UINT wDevID, DWORD dwFlags, LPMCI_DGV_STATUS_PARMSW lpParms) DECLSPEC_HIDDEN;
 
 /* mmoutput.c */
-BOOL	MCIAVI_GetInfo(WINE_MCIAVI* wma);
-DWORD	MCIAVI_OpenAudio(WINE_MCIAVI* wma, unsigned* nHdr, LPWAVEHDR* pWaveHdr);
-BOOL	MCIAVI_OpenVideo(WINE_MCIAVI* wma);
-void	MCIAVI_PlayAudioBlocks(WINE_MCIAVI* wma, unsigned nHdr, LPWAVEHDR waveHdr);
-LRESULT MCIAVI_PaintFrame(WINE_MCIAVI* wma, HDC hDC);
+BOOL	MCIAVI_GetInfo(WINE_MCIAVI* wma) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_OpenAudio(WINE_MCIAVI* wma, unsigned* nHdr, LPWAVEHDR* pWaveHdr) DECLSPEC_HIDDEN;
+BOOL	MCIAVI_OpenVideo(WINE_MCIAVI* wma) DECLSPEC_HIDDEN;
+void	MCIAVI_PlayAudioBlocks(WINE_MCIAVI* wma, unsigned nHdr, LPWAVEHDR waveHdr) DECLSPEC_HIDDEN;
+LRESULT MCIAVI_PaintFrame(WINE_MCIAVI* wma, HDC hDC) DECLSPEC_HIDDEN;
 
 /* mciavi.c */
-WINE_MCIAVI*	MCIAVI_mciGetOpenDev(UINT wDevID);
-DWORD MCIAVI_mciClose(UINT, DWORD, LPMCI_GENERIC_PARMS);
+WINE_MCIAVI*	MCIAVI_mciGetOpenDev(UINT wDevID) DECLSPEC_HIDDEN;
+DWORD MCIAVI_mciClose(UINT, DWORD, LPMCI_GENERIC_PARMS) DECLSPEC_HIDDEN;
 
 /* wnd.c */
-BOOL    MCIAVI_RegisterClass(void);
-BOOL    MCIAVI_UnregisterClass(void);
-BOOL    MCIAVI_CreateWindow(WINE_MCIAVI* wma, DWORD dwFlags, LPMCI_DGV_OPEN_PARMSW lpOpenParms);
-DWORD	MCIAVI_mciPut(UINT wDevID, DWORD dwFlags, LPMCI_DGV_PUT_PARMS lpParms);
-DWORD	MCIAVI_mciWhere(UINT wDevID, DWORD dwFlags, LPMCI_DGV_RECT_PARMS lpParms);
-DWORD	MCIAVI_mciWindow(UINT wDevID, DWORD dwFlags, LPMCI_DGV_WINDOW_PARMSW lpParms);
+BOOL    MCIAVI_RegisterClass(void) DECLSPEC_HIDDEN;
+BOOL    MCIAVI_UnregisterClass(void) DECLSPEC_HIDDEN;
+BOOL    MCIAVI_CreateWindow(WINE_MCIAVI* wma, DWORD dwFlags, LPMCI_DGV_OPEN_PARMSW lpOpenParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciPut(UINT wDevID, DWORD dwFlags, LPMCI_DGV_PUT_PARMS lpParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciWhere(UINT wDevID, DWORD dwFlags, LPMCI_DGV_RECT_PARMS lpParms) DECLSPEC_HIDDEN;
+DWORD	MCIAVI_mciWindow(UINT wDevID, DWORD dwFlags, LPMCI_DGV_WINDOW_PARMSW lpParms) DECLSPEC_HIDDEN;
 
 #endif  /* __WINE_PRIVATE_MCIAVI_H */