diff --git a/configure.ac b/configure.ac
index 7f8594ac7..6d68edec6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1676,7 +1676,7 @@ if test "x$XQUARTZ" = xyes; then
 
 	AC_CHECK_LIB([Xplugin],[xp_init],[:])
 
-	CFLAGS="${CFLAGS} -DROOTLESS_WORKAROUND -DNO_ALLOCA"
+	CFLAGS="${CFLAGS} -DROOTLESS_WORKAROUND -DROOTLESS_SAFEALPHA -DNO_ALLOCA"
 
 	PKG_CHECK_MODULES(XPBPROXY, [applewmproto >= 1.2] [applewm >= 1.2] xfixes fixesproto x11)
 
diff --git a/mi/miexpose.c b/mi/miexpose.c
index 2fba6a28c..961c35c38 100644
--- a/mi/miexpose.c
+++ b/mi/miexpose.c
@@ -535,7 +535,7 @@ _X_EXPORT void
 miPaintWindow(WindowPtr pWin, RegionPtr prgn, int what)
 {
     ScreenPtr	pScreen = pWin->drawable.pScreen;
-    ChangeGCVal gcval[5];
+    ChangeGCVal gcval[6];
     BITS32	gcmask;
     GCPtr	pGC;
     int		i;
@@ -603,18 +603,35 @@ miPaintWindow(WindowPtr pWin, RegionPtr prgn, int what)
     gcval[0].val = GXcopy;
     gcmask = GCFunction;
 
+#ifdef ROOTLESS_SAFEALPHA
+/* Bit mask for alpha channel with a particular number of bits per
+ * pixel. Note that we only care for 32bpp data. Mac OS X uses planar
+ * alpha for 16bpp.
+ */
+#define RootlessAlphaMask(bpp) ((bpp) == 32 ? 0xFF000000 : 0)
+#endif
+    
     if (solid)
     {
+#ifdef ROOTLESS_SAFEALPHA
+	gcval[1].val = fill.pixel | RootlessAlphaMask(pWin->drawable.bitsPerPixel);
+#else
 	gcval[1].val = fill.pixel;
+#endif
 	gcval[2].val  = FillSolid;
 	gcmask |= GCForeground | GCFillStyle;
     }
     else
     {
-	gcval[1].val = FillTiled;
-	gcval[2].ptr = (pointer)fill.pixmap;
-	gcval[3].val = tile_x_off;
-	gcval[4].val = tile_y_off;
+	int c=1;
+#ifdef ROOTLESS_SAFEALPHA
+	gcval[c++].val = ((CARD32)-1) & ~RootlessAlphaMask(pWin->drawable.bitsPerPixel);
+	gcmask |= GCPlaneMask;
+#endif
+	gcval[c++].val = FillTiled;
+	gcval[c++].ptr = (pointer)fill.pixmap;
+	gcval[c++].val = tile_x_off;
+	gcval[c++].val = tile_y_off;
 	gcmask |= GCFillStyle | GCTile | GCTileStipXOrigin | GCTileStipYOrigin;
     }