diff --git a/Xi/exevents.c b/Xi/exevents.c
index ad3d4290b..af98bac04 100644
--- a/Xi/exevents.c
+++ b/Xi/exevents.c
@@ -83,8 +83,6 @@ SOFTWARE.
 	Mod3Mask | Mod4Mask | Mod5Mask )
 #define AllButtonsMask ( \
 	Button1Mask | Button2Mask | Button3Mask | Button4Mask | Button5Mask )
-#define Motion_Filter(class) (DevicePointerMotionMask | \
-			      (class)->state | (class)->motionMask)
 
 Bool ShouldFreeInputMasks(WindowPtr /* pWin */ ,
 				 Bool	/* ignoreSelectedEvents */
@@ -832,6 +830,7 @@ UpdateDeviceState(DeviceIntPtr device, xEvent* xE, int count)
 	    device->valuator->motionHintWindow = NullWindow;
 	*kptr &= ~bit;
     } else if (xE->u.u.type == DeviceButtonPress) {
+        Mask mask;
         if (!b)
             return DONT_PROCESS;
 
@@ -847,8 +846,15 @@ UpdateDeviceState(DeviceIntPtr device, xEvent* xE, int count)
 	b->motionMask = DeviceButtonMotionMask;
         if (b->map[key] <= 5)
 	    b->state |= (Button1Mask >> 1) << b->map[key];
-	SetMaskForEvent(device->id, Motion_Filter(b), DeviceMotionNotify);
+
+        /* Add state and motionMask to the filter for this event */
+        mask = DevicePointerMotionMask | b->state | b->motionMask;
+        SetMaskForEvent(device->id, mask, DeviceMotionNotify);
+        mask = PointerMotionMask | b->state | b->motionMask;
+        SetMaskForEvent(device->id, mask, MotionNotify);
     } else if (xE->u.u.type == DeviceButtonRelease) {
+        Mask mask;
+
         if (!b)
             return DONT_PROCESS;
 
@@ -879,7 +885,12 @@ UpdateDeviceState(DeviceIntPtr device, xEvent* xE, int count)
 	    b->motionMask = 0;
 	if (b->map[key] <= 5)
 	    b->state &= ~((Button1Mask >> 1) << b->map[key]);
-	SetMaskForEvent(device->id, Motion_Filter(b), DeviceMotionNotify);
+
+        /* Add state and motionMask to the filter for this event */
+        mask = DevicePointerMotionMask | b->state | b->motionMask;
+        SetMaskForEvent(device->id, mask, DeviceMotionNotify);
+        mask = PointerMotionMask | b->state | b->motionMask;
+        SetMaskForEvent(device->id, mask, MotionNotify);
     } else if (xE->u.u.type == ProximityIn)
 	device->valuator->mode &= ~OutOfProximity;
     else if (xE->u.u.type == ProximityOut)
diff --git a/dix/events.c b/dix/events.c
index 598dc7514..ae566c539 100644
--- a/dix/events.c
+++ b/dix/events.c
@@ -190,13 +190,6 @@ typedef const char *string;
  * See DeliverEventsToWindow().
  */
 #define ImplicitGrabMask (1 << 7)
-/*
- * The following relies on the fact that the Button<n>MotionMasks are equal
- * to the corresponding Button<n>Masks from the current modifier/button state.
- */
-#define Motion_Filter(class) (PointerMotionMask | \
-			      (class)->state | (class)->motionMask)
-
 
 #define WID(w) ((w) ? ((w)->drawable.id) : 0)
 
@@ -571,20 +564,26 @@ XineramaConfineCursorToWindow(DeviceIntPtr pDev,
 
 #endif  /* PANORAMIX */
 
+/**
+ * Modifies the filter for the given protocol event type to the given masks.
+ *
+ * There's only two callers: UpdateDeviceState() and XI's SetMaskForExtEvent().
+ * The latter initialises masks for the matching XI events, it's a once-off
+ * setting.
+ * UDS however changes the mask for MotionNotify and DeviceMotionNotify each
+ * time a button is pressed to include the matching ButtonXMotion mask in the
+ * filter.
+ *
+ * @param[in] deviceid The device to modify the filter for.
+ * @param[in] mask The new filter mask.
+ * @param[in] event Protocol event type.
+ */
 void
 SetMaskForEvent(int deviceid, Mask mask, int event)
 {
-    int coretype;
     if (deviceid < 0 || deviceid > MAXDEVICES)
         FatalError("SetMaskForEvent: bogus device id");
-    if ((event < LASTEvent) || (event >= 128))
-	FatalError("SetMaskForEvent: bogus event number");
     filters[deviceid][event] = mask;
-
-    /* Need to change the mask for the core events too */
-    coretype = XItoCoreType(event);
-    if (coretype)
-        filters[deviceid][coretype] = mask;
 }
 
 void
@@ -4618,6 +4617,8 @@ InitEvents(void)
     inputInfo.keyboard = (DeviceIntPtr)NULL;
     inputInfo.pointer = (DeviceIntPtr)NULL;
     lastEventMask = OwnerGrabButtonMask;
+    /* The mask for pointer motion events may have changed in the last server
+     * generation. See comment above definition of filters. */
     filters[0][PointerMotionMask] = MotionNotify;
     for (i = 1; i < MAXDEVICES; i++)
     {
diff --git a/include/dix.h b/include/dix.h
index 8d6b9ff44..204dcf296 100644
--- a/include/dix.h
+++ b/include/dix.h
@@ -304,7 +304,7 @@ extern _X_EXPORT void SetVendorString(char *string);
 
 /* events.c */
 
-extern _X_EXPORT void SetMaskForEvent(
+extern void SetMaskForEvent(
     int /* deviceid */,
     Mask /* mask */,
     int /* event */);