diff --git a/block.c b/block.c
index d85e27e43c..15f807a0ca 100644
--- a/block.c
+++ b/block.c
@@ -54,6 +54,8 @@ static int bdrv_read_em(BlockDriverState *bs, int64_t sector_num,
 static int bdrv_write_em(BlockDriverState *bs, int64_t sector_num,
                          const uint8_t *buf, int nb_sectors);
 
+BlockDriverState *bdrv_first;
+
 static BlockDriver *first_drv;
 
 int path_is_absolute(const char *path)
diff --git a/block_int.h b/block_int.h
index 137000e140..7f1a514063 100644
--- a/block_int.h
+++ b/block_int.h
@@ -145,6 +145,6 @@ void *qemu_aio_get(BlockDriverState *bs, BlockDriverCompletionFunc *cb,
                    void *opaque);
 void qemu_aio_release(void *p);
 
-BlockDriverState *bdrv_first;
+extern BlockDriverState *bdrv_first;
 
 #endif /* BLOCK_INT_H */
diff --git a/hw/arm-misc.h b/hw/arm-misc.h
index f118edb3bd..a147254287 100644
--- a/hw/arm-misc.h
+++ b/hw/arm-misc.h
@@ -37,7 +37,7 @@ void arm_load_kernel(CPUState *env, struct arm_boot_info *info);
 
 /* Multiplication factor to convert from system clock ticks to qemu timer
    ticks.  */
-int system_clock_scale;
+extern int system_clock_scale;
 qemu_irq *armv7m_nvic_init(CPUState *env);
 
 /* stellaris_enent.c */
diff --git a/hw/armv7m_nvic.c b/hw/armv7m_nvic.c
index c55c958718..86d0cf8f9e 100644
--- a/hw/armv7m_nvic.c
+++ b/hw/armv7m_nvic.c
@@ -50,6 +50,8 @@ typedef struct {
 #define SYSTICK_CLKSOURCE (1 << 2)
 #define SYSTICK_COUNTFLAG (1 << 16)
 
+int system_clock_scale;
+
 /* Conversion factor from qemu timer to SysTick frequencies.  */
 static inline int64_t systick_scale(nvic_state *s)
 {