diff --git a/sysmoOCTSIM/config/peripheral_clk_config.h b/sysmoOCTSIM/config/peripheral_clk_config.h
index f794792..6d8ba10 100644
--- a/sysmoOCTSIM/config/peripheral_clk_config.h
+++ b/sysmoOCTSIM/config/peripheral_clk_config.h
@@ -12,6 +12,22 @@
 #define CONF_CPU_FREQUENCY 120000000
 #endif
 
+// <y> RTC Clock Source
+// <id> rtc_clk_selection
+// <RTC_CLOCK_SOURCE"> RTC source
+// <i> Select the clock source for RTC.
+#ifndef CONF_GCLK_RTC_SRC
+#define CONF_GCLK_RTC_SRC RTC_CLOCK_SOURCE
+#endif
+
+/**
+ * \def CONF_GCLK_RTC_FREQUENCY
+ * \brief RTC's Clock frequency
+ */
+#ifndef CONF_GCLK_RTC_FREQUENCY
+#define CONF_GCLK_RTC_FREQUENCY 32768
+#endif
+
 // <y> Core Clock Source
 // <id> core_gclk_selection