diff --git a/tests/python/render_layer/render_layer_common.py b/tests/python/render_layer/render_layer_common.py
index 683f8c5ccff..7e8cbf988c8 100644
--- a/tests/python/render_layer/render_layer_common.py
+++ b/tests/python/render_layer/render_layer_common.py
@@ -159,6 +159,7 @@ def dump(data):
 
 PDB = False
 DUMP_DIFF = True
+UPDATE_DIFF = False # HACK used to update tests when something change
 
 
 def compare_files(file_a, file_b):
@@ -172,6 +173,11 @@ def compare_files(file_a, file_b):
             import subprocess
             subprocess.call(["diff", "-u", file_a, file_b])
 
+        if UPDATE_DIFF:
+            import subprocess
+            subprocess.call(["cp", "-u", file_a, file_b])
+
+
         if PDB:
             import pdb
             print("Files differ:", file_a, file_b)