diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h
index c649108a9e9f298c4266c568ce88627bd8e2eab9..07176d92e1c92789daf5c75df5c901d7605bd5c5 100644
--- a/arch/um/include/kern_util.h
+++ b/arch/um/include/kern_util.h
@@ -31,8 +31,6 @@ extern int timer_irq_inited;
 extern int jail;
 extern int nsyscalls;
 
-extern struct task_struct *idle_threads[NR_CPUS];
-
 #define UML_ROUND_DOWN(addr) ((void *)(((unsigned long) addr) & PAGE_MASK))
 #define UML_ROUND_UP(addr) \
 	UML_ROUND_DOWN(((unsigned long) addr) + PAGE_SIZE - 1)
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 6f1a3a288117985e1b4bc9d73bda578284c26d09..3ef73bf2e781a79dbd039c623fc20c3dd3f289d5 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -5,6 +5,7 @@
 
 #include "linux/module.h"
 #include "linux/sched.h"
+#include "asm/smp.h"
 #include "user_util.h"
 #include "kern_util.h"
 #include "kern.h"
diff --git a/include/asm-um/smp.h b/include/asm-um/smp.h
index d879eba2b52c7d74e646a3213911304f877279c5..aeda6657f366e156ff8e6997f06a6726f19098ea 100644
--- a/include/asm-um/smp.h
+++ b/include/asm-um/smp.h
@@ -23,6 +23,8 @@ extern inline void smp_cpus_done(unsigned int maxcpus)
 {
 }
 
+extern struct task_struct *idle_threads[NR_CPUS];
+
 #endif
 
 #endif