diff --git a/test/libminijail_test.cpp b/test/libminijail_test.cpp
index 6499a37..e457c24 100644
--- a/test/libminijail_test.cpp
+++ b/test/libminijail_test.cpp
@@ -19,6 +19,7 @@
 #include <libminijail.h>
 
 #include <android-base/logging.h>
+#include <android-base/macros.h>
 
 const uid_t kSystemUid = 1000U;
 
@@ -114,7 +115,7 @@
   minijail* j = minijail_new();
   minijail_change_user(j, "system");
   minijail_change_group(j, "system");
-  size_t num_groups = sizeof(groups) / sizeof(groups[0]);
+  size_t num_groups = arraysize(groups);
   minijail_set_supplementary_gids(j, num_groups, groups);
   minijail_use_caps(j, CAP_TO_MASK(CAP_SETUID) | CAP_TO_MASK(CAP_SETGID));
   minijail_enter(j);