diff --git a/einkfb.c b/einkfb.c
index d7a594288..f4a10a8bb 100644
--- a/einkfb.c
+++ b/einkfb.c
@@ -108,7 +108,7 @@ inline void fillMxcfbUpdateData51(mxcfb_update_data51 *myarea, FBInfo *fb, lua_S
 	myarea->hist_gray_waveform_mode = 0;
 	myarea->temp = 0x1001;
 	myarea->flags = 0;
-	myarea->alt_buffer_data.virt_addr = NULL;
+	/*myarea->alt_buffer_data.virt_addr = NULL;*/
 	myarea->alt_buffer_data.phys_addr = NULL;
 	myarea->alt_buffer_data.width = 0;
 	myarea->alt_buffer_data.height = 0;
@@ -141,7 +141,7 @@ void kindle51einkUpdate(FBInfo *fb, lua_State *L) {
 	fb4BppTo8Bpp(fb);
 	fillMxcfbUpdateData51(&myarea, fb, L);
 
-	ioctl(fb->fd, 0x4048462e, &myarea);
+	ioctl(fb->fd, MXCFB_SEND_UPDATE51, &myarea);
 }
 #endif	
 
diff --git a/include/mxcfb.h b/include/mxcfb.h
index e4e885bf8..4e313299b 100644
--- a/include/mxcfb.h
+++ b/include/mxcfb.h
@@ -1,12 +1,15 @@
 /*
  * Copyright 2004-2011 Freescale Semiconductor, Inc. All Rights Reserved.
  *
- * Modified by houqp, added mxcfb_update_data51 struct from GeekMaster's video
- * player, refer to:
- * http://www.mobileread.com/forums/showthread.php?t=177455&page=10
- */
-
-/*
+ * - Modified by houqp, added mxcfb_update_data51 struct from GeekMaster's
+ *   video player, refer to:
+ *   http://www.mobileread.com/forums/showthread.php?t=177455&page=10
+ *
+ * - Modified mxcfb_alt_buffer_data struct according to include/linux/mxcfb.h
+ *   from Kindle 5.3.0 firmware. Thanks to eureka@mobileread.
+ *   http://www.mobileread.com/forums/showpost.php?p=2337118&postcount=818
+ *
+ *
  * The code contained herein is licensed under the GNU Lesser General
  * Public License.  You may obtain a copy of the GNU Lesser General
  * Public License Version 2.1 or later at the following locations:
@@ -96,7 +99,8 @@ struct mxcfb_rect {
 #define FB_TEMP_AUTO_UPDATE_DISABLE     -1
 
 struct mxcfb_alt_buffer_data {
-	void *virt_addr;
+	/* virt_addr is not included in amazon's source */
+	/* void *virt_addr; */
 	__u32 phys_addr;
 	__u32 width;	/* width of entire buffer */
 	__u32 height;	/* height of entire buffer */
@@ -168,6 +172,9 @@ struct mxcfb_waveform_modes {
 #define MXCFB_SET_TEMP_AUTO_UPDATE_PERIOD     _IOR('F', 0x36, int32_t)
 #define MXCFB_SET_MERGE_ON_WAVEFORM_MISMATCH	_IOW('F', 0x37, int32_t)
 
+/* IOCTLs for E-ink panel updates, kindle firmware version >= 5.1 */
+#define MXCFB_SEND_UPDATE51 _IOW('F', 0x2E, struct mxcfb_update_data51)
+
 #ifdef __KERNEL__
 
 extern struct fb_videomode mxcfb_modedb[];