diff --git a/adafruit_gfx/gfx.py b/adafruit_gfx/gfx.py
index 8c251c3..cf7feac 100755
--- a/adafruit_gfx/gfx.py
+++ b/adafruit_gfx/gfx.py
@@ -276,7 +276,7 @@ def fill_triangle(self, x0, y0, x1, y1, x2, y2, *args, **kwargs):
             dy12 = 1
         sa = 0
         sb = 0
-        if y1 == y2:
+        if y1 == y2 or y0 == y1:  # pylint: disable=consider-using-in
             last = y1
         else:
             last = y1 - 1