diff --git a/tests/run.sh b/tests/run.sh
index d3680b3b..8219445d 100755
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -45,7 +45,7 @@ if [ "$CI" = true ]; then
     TEST_PAUSE_ON_ERRORS=0
     TEST_QUIT_ON_TIMEOUT=1
 else
-    HEADLESS=0
+    HEADLESS=${HEADLESS-0}
     TEST_PAUSE_ON_ERRORS=${TEST_PAUSE_ON_ERRORS-0}
     TEST_QUIT_ON_TIMEOUT=1
 fi