Index: b/Tests/test_file_webp.py
===================================================================
--- a/Tests/test_file_webp.py
+++ b/Tests/test_file_webp.py
@@ -1,6 +1,7 @@
 from tester import *
 
 from PIL import Image
+import os
 
 try:
     from PIL import _webp
@@ -27,7 +28,11 @@
     assert_no_exception(lambda: image.getdata())
 
     # generated with: dwebp -ppm ../../Images/lena.webp -o lena_webp_bits.ppm
-    target = Image.open('Tests/images/lena_webp_bits.ppm')
+    if 'ADTTMP' in os.environ:
+        target = Image.open(os.path.join(os.environ['ADTTMP'], 'lena_webp.ppm'))
+    else:
+        target = Image.open('Tests/images/lena_webp_bits.ppm')
+
     assert_image_equal(image, target)
 
 
