diff --git a/src/devctxt.c b/src/devctxt.c
index e858330..2fd12a4 100755
--- a/src/devctxt.c
+++ b/src/devctxt.c
@@ -69,13 +69,13 @@ static BOOL line_clip(PINT32 output, INT32 x1, INT32 y1, INT32 x2, INT32 y2, INT
 	}
 	else if (outcode1 & 0x2)
 	{
-	  y1 += (y2 - y1) * ((xmax - x1) / (x2 - x1));
+	  y1 -= (y2 - y1) * ((xmax - x1) / (x2 - x1));
 	  x1 = xmax;
 	  Log(LDEBUG, "clipped against right to point (%d, %d)", x1 >> 16, y1 >> 16);
 	}
 	else if (outcode1 & 0x1)
 	{
-	  y1 += (y2 - y1) * ((xmin - x1) / (x2 - x1));
+	  y1 -= (y2 - y1) * ((xmin - x1) / (x2 - x1));
 	  x1 = xmin;
 	  Log(LDEBUG, "clipped against left to point (%d, %d)", x1 >> 16, y1 >> 16);
 	}