diff --git a/tests/qemu-iotests/052 b/tests/qemu-iotests/052
index 6bdae92..61959e2 100755
--- a/tests/qemu-iotests/052
+++ b/tests/qemu-iotests/052
@@ -41,8 +41,9 @@
 _supported_fmt generic
 _supported_proto file
 _supported_os Linux
-_default_cache_mode "writethrough"
-_supported_cache_modes "writethrough"
+
+# Don't do O_DIRECT on tmpfs
+_supported_cache_modes "writeback" "writethrough" "unsafe"
 
 size=128M
 _make_test_img $size