diff --git a/tests/testutils.c b/tests/testutils.c
index 4fb2338bb1..4b8cf79ef9 100644
--- a/tests/testutils.c
+++ b/tests/testutils.c
@@ -240,7 +240,7 @@ virTestRun(const char *title,
         for (i = start; i < end; i++) {
             bool missingFail = false;
 # ifdef TEST_OOM_TRACE
-            memset(testAllocStack, 0, ARRAY_CARDINALITY(testAllocStack));
+            memset(testAllocStack, 0, sizeof(testAllocStack));
             ntestAllocStack = 0;
 # endif
             virAllocTestOOM(i + 1, 1);