diff --git a/arch/sim/src/sim/up_internal.h b/arch/sim/src/sim/up_internal.h
index 7208e314be..de35b8cc19 100644
--- a/arch/sim/src/sim/up_internal.h
+++ b/arch/sim/src/sim/up_internal.h
@@ -211,8 +211,8 @@
  * so that it will be ready for the next pause operation.
  */
 
-volatile spinlock_t g_cpu_wait[CONFIG_SMP_NCPUS] SP_SECTION;
-volatile spinlock_t g_cpu_paused[CONFIG_SMP_NCPUS] SP_SECTION;
+extern volatile spinlock_t g_cpu_wait[CONFIG_SMP_NCPUS] SP_SECTION;
+extern volatile spinlock_t g_cpu_paused[CONFIG_SMP_NCPUS] SP_SECTION;
 #endif
 
 /****************************************************************************