diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c
index 440aee705ccc..30e00ef0bf2e 100644
--- a/lib/memcpy_kunit.c
+++ b/lib/memcpy_kunit.c
@@ -32,7 +32,7 @@ struct some_bytes {
 	BUILD_BUG_ON(sizeof(instance.data) != 32);	\
 	for (size_t i = 0; i < sizeof(instance.data); i++) {	\
 		KUNIT_ASSERT_EQ_MSG(test, instance.data[i], v, \
-			"line %d: '%s' not initialized to 0x%02x @ %d (saw 0x%02x)\n", \
+			"line %d: '%s' not initialized to 0x%02x @ %zu (saw 0x%02x)\n", \
 			__LINE__, #instance, v, i, instance.data[i]);	\
 	}	\
 } while (0)
@@ -41,7 +41,7 @@ struct some_bytes {
 	BUILD_BUG_ON(sizeof(one) != sizeof(two)); \
 	for (size_t i = 0; i < sizeof(one); i++) {	\
 		KUNIT_EXPECT_EQ_MSG(test, one.data[i], two.data[i], \
-			"line %d: %s.data[%d] (0x%02x) != %s.data[%d] (0x%02x)\n", \
+			"line %d: %s.data[%zu] (0x%02x) != %s.data[%zu] (0x%02x)\n", \
 			__LINE__, #one, i, one.data[i], #two, i, two.data[i]); \
 	}	\
 	kunit_info(test, "ok: " TEST_OP "() " name "\n");	\