diff --git a/src/devctxt.c b/src/devctxt.c
index 130b7de..f6fb92b 100755
--- a/src/devctxt.c
+++ b/src/devctxt.c
@@ -76,14 +76,14 @@ static BOOL line_clip(PINT32 output, INT32 x1, INT32 y1, INT32 x2, INT32 y2, INT
 	else if (outcode1 & 0x2)
 	{
 	  tmp = M(y2 - y1, D(xmax - x1, x2 - x1));
-	  y1 -= tmp;
+	  y1 += tmp;
 	  x1 = xmax;
 	  Log(LDEBUG, "clipped against right to point (%d, %d), dy=%d/%d", x1 >> CPX, y1 >> CPX, tmp >> CPX, tmp);
 	}
 	else if (outcode1 & 0x1)
 	{
 	  tmp = M(y2 - y1, D(xmin - x1, x2 - x1));
-	  y1 -= tmp;
+	  y1 += tmp;
 	  x1 = xmin;
 	  Log(LDEBUG, "clipped against left to point (%d, %d), dy=%d/%d", x1 >> CPX, y1 >> CPX, tmp >> CPX, tmp);
 	}