diff --git a/dlls/gdiplus/graphics.c b/dlls/gdiplus/graphics.c
index acee695e9fc..6635deac56a 100644
--- a/dlls/gdiplus/graphics.c
+++ b/dlls/gdiplus/graphics.c
@@ -1594,9 +1594,9 @@ static void draw_cap(GpGraphics *graphics, COLORREF color, GpLineCap cap, REAL s
             ptf[3].X = x2 - dbig;
             ptf[2].X = x2 + dsmall;
 
-            gdip_transform_points(graphics, WineCoordinateSpaceGdiDevice, CoordinateSpaceWorld, ptf, 3);
+            gdip_transform_points(graphics, WineCoordinateSpaceGdiDevice, CoordinateSpaceWorld, ptf, 4);
 
-            round_points(pt, ptf, 3);
+            round_points(pt, ptf, 4);
 
             Polygon(graphics->hdc, pt, 4);