diff --git a/include/mmsystem.h b/include/mmsystem.h
index 310a6f4de19..c8e7f4d2de4 100644
--- a/include/mmsystem.h
+++ b/include/mmsystem.h
@@ -2787,7 +2787,21 @@ typedef struct {
 	UINT16	wCustomCommandTable;	/* custom command table (0xFFFF if none)
 											 * filled in by the driver */
 	UINT16	wType;			/* driver type (filled in by the driver) */
-} MCI_OPEN_DRIVER_PARMS, *LPMCI_OPEN_DRIVER_PARMS;
+} MCI_OPEN_DRIVER_PARMS16, *LPMCI_OPEN_DRIVER_PARMS16;
+
+typedef struct {
+	UINT	wDeviceID;		/* device ID */
+	LPSTR	lpstrParams;	/* parameter string for entry in SYSTEM.INI */
+	UINT	wCustomCommandTable;	/* custom command table (0xFFFF if none) * filled in by the driver */
+	UINT	wType;			/* driver type (filled in by the driver) */
+} MCI_OPEN_DRIVER_PARMSA, *LPMCI_OPEN_DRIVER_PARMSA;
+
+typedef struct {
+	UINT	wDeviceID;		/* device ID */
+	LPWSTR	lpstrParams;	/* parameter string for entry in SYSTEM.INI */
+	UINT	wCustomCommandTable;	/* custom command table (0xFFFF if none) * filled in by the driver */
+	UINT	wType;			/* driver type (filled in by the driver) */
+} MCI_OPEN_DRIVER_PARMSW, *LPMCI_OPEN_DRIVER_PARMSW;
 
 DWORD  WINAPI mciGetDriverData16(UINT16 uDeviceID);
 DWORD  WINAPI mciGetDriverData(UINT uDeviceID);
diff --git a/include/multimedia.h b/include/multimedia.h
index b8245fdec84..3a2d3b5258d 100644
--- a/include/multimedia.h
+++ b/include/multimedia.h
@@ -42,11 +42,11 @@
 #endif
 
 struct WINE_MCIDRIVER {
-	HDRVR16						hDrv;
-	DRIVERPROC16				driverProc;
-	MCI_OPEN_DRIVER_PARMS	modp;
-	MCI_OPEN_PARMS16			mop;
-	DWORD							dwPrivate;
+	HDRVR16			hDrv;
+	DRIVERPROC16		driverProc;
+	MCI_OPEN_DRIVER_PARMS16	modp;
+	MCI_OPEN_PARMS16	mop;
+	DWORD			dwPrivate;
 };
 
 /* function prototypes */