--- ./nx-X11/programs/Xserver/dix/pixmap.c.X.original	2015-02-13 14:03:44.704442298 +0100
+++ ./nx-X11/programs/Xserver/dix/pixmap.c	2015-02-10 19:13:13.696689930 +0100
@@ -121,7 +121,14 @@
     if (pScreen->totalPixmapSize > ((size_t)-1) - pixDataSize)
 	return NullPixmap;
     
-    pPixmap = (PixmapPtr)xalloc(pScreen->totalPixmapSize + pixDataSize);
+    /*
+     * FIXME: Allocate 4 bytes at the end of each pixmap. This
+     * is a quick workaround intended to fix a problem reported
+     * by Valgrind due to fbBlt() writing just after the end of
+     * the pixmap buffer. This may be a RENDER bug.
+     */
+
+    pPixmap = (PixmapPtr)xalloc(pScreen->totalPixmapSize + pixDataSize + 4);
     if (!pPixmap)
 	return NullPixmap;
     ppriv = (DevUnion *)(pPixmap + 1);