diff --git a/drivers/rtc/lib_test.c b/drivers/rtc/lib_test.c
index d5caf36c56cd..225c859d6da5 100644
--- a/drivers/rtc/lib_test.c
+++ b/drivers/rtc/lib_test.c
@@ -54,7 +54,7 @@ static void rtc_time64_to_tm_test_date_range(struct kunit *test)
 
 		days = div_s64(secs, 86400);
 
-		#define FAIL_MSG "%d/%02d/%02d (%2d) : %ld", \
+		#define FAIL_MSG "%d/%02d/%02d (%2d) : %lld", \
 			year, month, mday, yday, days
 
 		KUNIT_ASSERT_EQ_MSG(test, year - 1900, result.tm_year, FAIL_MSG);