diff --git a/include/dt-bindings/clock/at91.h b/include/dt-bindings/clock/at91.h
index 6ede88c3992d1..99f4767ff6bb4 100644
--- a/include/dt-bindings/clock/at91.h
+++ b/include/dt-bindings/clock/at91.h
@@ -55,4 +55,8 @@
 #define AT91_PMC_GCKRDY		24		/* Generated Clocks */
 #endif
 
+/* Slow clock. */
+#define SCKC_MD_SLCK		0
+#define SCKC_TD_SLCK		1
+
 #endif