diff --git a/hw/dmx/input/dmxcommon.c b/hw/dmx/input/dmxcommon.c
index da5b77893..2f23d1c9b 100644
--- a/hw/dmx/input/dmxcommon.c
+++ b/hw/dmx/input/dmxcommon.c
@@ -370,7 +370,7 @@ void dmxCommonOthGetInfo(DevicePtr pDev, DMXLocalInitInfoPtr info)
     Display              *display = priv->display;
     int                  num;
     int                  i, j, k;
-    int                  (*handler)(Display *, char *, char *);
+    XextErrorHandler     handler;
 
     if (!display && !(display = XOpenDisplay(dmxInput->name)))
         return;
diff --git a/hw/dmx/input/dmxinputinit.c b/hw/dmx/input/dmxinputinit.c
index 5943e9248..1242be1bd 100644
--- a/hw/dmx/input/dmxinputinit.c
+++ b/hw/dmx/input/dmxinputinit.c
@@ -827,7 +827,7 @@ static void dmxPopulateLocal(DMXInputInfo *dmxInput, dmxArg a)
     }
 }
 
-int dmxInputExtensionErrorHandler(Display *dsp, char *name, char *reason)
+int dmxInputExtensionErrorHandler(Display *dsp, _Xconst char *name, _Xconst char *reason)
 {
     return 0;
 }
@@ -839,7 +839,7 @@ static void dmxInputScanForExtensions(DMXInputInfo *dmxInput, int doXI)
     Display              *display;
     int                  num;
     int                  i, j;
-    int                  (*handler)(Display *, char *, char *);
+    XextErrorHandler     handler;
 
     if (!(display = XOpenDisplay(dmxInput->name))) return;
     
diff --git a/hw/dmx/input/dmxinputinit.h b/hw/dmx/input/dmxinputinit.h
index 2e625cfd4..5a4a4106c 100644
--- a/hw/dmx/input/dmxinputinit.h
+++ b/hw/dmx/input/dmxinputinit.h
@@ -276,8 +276,8 @@ extern void dmxKeyboardKbdCtrlProc(DeviceIntPtr pDevice, KeybdCtrl *ctrl);
 extern void dmxKeyboardBellProc(int percent, DeviceIntPtr pDevice,
                                 pointer ctrl, int unknown);
 
-extern int  dmxInputExtensionErrorHandler(Display *dsp, char *name,
-                                          char *reason);
+extern int  dmxInputExtensionErrorHandler(Display *dsp, _Xconst char *name,
+                                          _Xconst char *reason);
 
 extern int          dmxInputDetach(DMXInputInfo *dmxInput);
 extern void         dmxInputDetachAll(DMXScreenInfo *dmxScreen);