diff --git a/arch/arm/mach-at91/include/mach/clk.h b/arch/arm/mach-at91/include/mach/clk.h
index c1d92739e47..09b8f0586c6 100644
--- a/arch/arm/mach-at91/include/mach/clk.h
+++ b/arch/arm/mach-at91/include/mach/clk.h
@@ -11,6 +11,7 @@
 #include <asm/arch/hardware.h>
 #include <asm/arch/at91_pmc.h>
 #include <asm/global_data.h>
+#include <asm/io.h>
 
 #define GCK_CSS_SLOW_CLK	0
 #define GCK_CSS_MAIN_CLK	1