diff --git a/parallel-rdp/interface.cpp b/parallel-rdp/interface.cpp
index 6a5c89f5..b2eec742 100644
--- a/parallel-rdp/interface.cpp
+++ b/parallel-rdp/interface.cpp
@@ -332,38 +332,27 @@ bool rdp_update_screen()
 
 static uint32_t viCalculateHorizonalWidth(uint32_t hstart, uint32_t xscale, uint32_t width)
 {
-	if (xscale == 0)
-		return 320;
-
-	uint32_t start = ((hstart & 0x03FF0000) >> 16) & 0x3FF;
+	uint32_t start = (hstart >> 16) & 0x3FF;
 	uint32_t end = (hstart & 0x3FF);
 	uint32_t delta;
 	if (end > start)
 		delta = end - start;
 	else
-		delta = start - end;
+		delta = 0;
 	uint32_t scale = (xscale & 0xFFF);
 
-	if (delta == 0)
-	{
-		delta = width;
-	}
-
 	return (delta * scale) / 0x400;
 }
 
 static uint32_t viCalculateVerticalHeight(uint32_t vstart, uint32_t yscale)
 {
-	if (yscale == 0)
-		return 240;
-
-	uint32_t start = ((vstart & 0x03FF0000) >> 16) & 0x3FF;
+	uint32_t start = (vstart >> 16) & 0x3FF;
 	uint32_t end = (vstart & 0x3FF);
 	uint32_t delta;
 	if (end > start)
 		delta = end - start;
 	else
-		delta = start - end;
+		delta = 0;
 	uint32_t scale = (yscale & 0xFFF);
 
 	return (delta * scale) / 0x800;