diff --git a/Arduino/epd4in2b_V2/epd4in2b_V2.cpp b/Arduino/epd4in2b_V2/epd4in2b_V2.cpp
index 94a8b2026..a9f0cc6a2 100644
--- a/Arduino/epd4in2b_V2/epd4in2b_V2.cpp
+++ b/Arduino/epd4in2b_V2/epd4in2b_V2.cpp
@@ -104,7 +104,7 @@ void Epd::SetPartialWindow(const unsigned char* buffer_black, const unsigned cha
     SendCommand(PARTIAL_WINDOW);
     SendData(x >> 8);
     SendData(x & 0xf8);     // x should be the multiple of 8, the last 3 bit will always be ignored
-    SendData(((x & 0xf8) + w  - 1) >> 8);
+    SendData((x + w  - 1) >> 8);
     SendData(((x & 0xf8) + w  - 1) | 0x07);
     SendData(y >> 8);        
     SendData(y & 0xff);
@@ -137,7 +137,7 @@ void Epd::SetPartialWindowBlack(const unsigned char* buffer_black, int x, int y,
     SendCommand(PARTIAL_WINDOW);
     SendData(x >> 8);
     SendData(x & 0xf8);     // x should be the multiple of 8, the last 3 bit will always be ignored
-    SendData(((x & 0xf8) + w  - 1) >> 8);
+    SendData((x + w  - 1) >> 8);
     SendData(((x & 0xf8) + w  - 1) | 0x07);
     SendData(y >> 8);        
     SendData(y & 0xff);