diff --git a/clutter/tests/conform/Makefile.am b/clutter/tests/conform/Makefile.am
index 369e1c1c1..9cef08b29 100644
--- a/clutter/tests/conform/Makefile.am
+++ b/clutter/tests/conform/Makefile.am
@@ -79,7 +79,7 @@ script_tests = \
 	test-script-timeline-markers.json \
 	test-state-1.json
 
-TESTS_ENVIRONMENT += G_ENABLE_DIAGNOSTIC=0 CLUTTER_ENABLE_DIAGNOSTIC=0
+TESTS_ENVIRONMENT += G_ENABLE_DIAGNOSTIC=0 CLUTTER_ENABLE_DIAGNOSTIC=0 CLUTTER_SCALE=1
 
 # simple rules for generating a Git ignore file for the conformance test suite
 $(srcdir)/.gitignore: Makefile