diff --git a/util/test/rdtest/util.py b/util/test/rdtest/util.py
index 368e54177..94aaeef4d 100644
--- a/util/test/rdtest/util.py
+++ b/util/test/rdtest/util.py
@@ -131,8 +131,16 @@ def png_compare(test_img: str, ref_img: str, tolerance: int = 2):
     test_reader = png.Reader(filename=test_img)
     ref_reader = png.Reader(filename=ref_img)
 
-    test_w, test_h, test_data, _ = test_reader.read()
-    ref_w, ref_h, ref_data, _ = ref_reader.read()
+    test_w, test_h, test_data, test_info = test_reader.read()
+    ref_w, ref_h, ref_data, ref_info = ref_reader.read()
+
+    # lookup rgba data straight
+    rgba_get = lambda data, x: data[x]
+    # lookup rgb data and return 255 for alpha
+    rgb_get = lambda data, x: data[ (x >> 2)*3 + (x % 4) ] if (x % 4) < 3 else 255
+
+    test_get = (rgba_get if test_info['alpha'] else rgb_get)
+    ref_get = (rgba_get if ref_info['alpha'] else rgb_get)
 
     if test_w != ref_w or test_h != test_h:
         return False
@@ -141,7 +149,8 @@ def png_compare(test_img: str, ref_img: str, tolerance: int = 2):
     diff_data = []
 
     for test_row, ref_row in zip(test_data, ref_data):
-        diff = [min(255, abs(test_row[i] - ref_row[i])*4) for i in range(0, test_w*4)]
+
+        diff = [min(255, abs(test_get(test_row, i) - ref_get(ref_row, i))*4) for i in range(0, test_w*4)]
 
         is_same = is_same and not any([d > tolerance*4 for d in diff])