diff --git a/src/tftlcd.c b/src/tftlcd.c
index 1b59a47..eaa8719 100644
--- a/src/tftlcd.c
+++ b/src/tftlcd.c
@@ -253,7 +253,8 @@ void LCD_DrawPoint(uint16_t x, uint16_t y, uint16_t color) {
 }
 
 void LCD_DrawLine(uint16_t x1, uint16_t y1, uint16_t x2, uint16_t y2) {
-    uint16_t x, y, d, dx, dy, xe, ye, Dx, Dy;
+    int16_t Dx, Dy;
+    uint16_t x, y, d, dx, dy, xe, ye;
 
     xe = ye = 0;
     x = x1, y = y1;