diff --git a/arch/arm/src/armv7-a/svcall.h b/arch/arm/src/armv7-a/svcall.h
index d22fde1c87b..84fb88ab7d0 100644
--- a/arch/arm/src/armv7-a/svcall.h
+++ b/arch/arm/src/armv7-a/svcall.h
@@ -29,6 +29,14 @@
 
 #include <syscall.h>
 
+/* SYS call 2:
+ *
+ * void arm_switchcontext(uint32_t *saveregs, uint32_t *restoreregs);
+ */
+
+#define SYS_switch_context        (2)
+
+
 #ifdef CONFIG_LIB_SYSCALL
 
 /****************************************************************************