diff --git a/sys/arm/at91/files.at91 b/sys/arm/at91/files.at91
index 0795eae928df..0ffb2cb7d115 100644
--- a/sys/arm/at91/files.at91
+++ b/sys/arm/at91/files.at91
@@ -6,6 +6,7 @@ arm/at91/at91_st.c		standard
 arm/at91/at91_mci.c		optional	at91_mci
 arm/at91/at91_pio.c		standard
 arm/at91/at91_pmc.c		standard
+arm/at91/at91_rtc.c		standard
 arm/at91/at91_ssc.c		optional	at91_ssc
 arm/at91/at91_spi.c		optional	at91_spi
 arm/at91/at91_twi.c		optional	at91_twi