diff --git a/tests/fortify_test.cpp b/tests/fortify_test.cpp
index 3a1bb93..abe2cae 100644
--- a/tests/fortify_test.cpp
+++ b/tests/fortify_test.cpp
@@ -350,7 +350,7 @@
   ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   char buf[10];
   memcpy(buf, "0123456789", sizeof(buf));
-  ASSERT_EXIT(printf("%d", strlen(buf)), testing::KilledBySignal(SIGABRT), "");
+  ASSERT_EXIT(printf("%zd", strlen(buf)), testing::KilledBySignal(SIGABRT), "");
 }
 
 TEST(DEATHTEST, strchr_fortified) {