2 files changed, 2 insertions, 2 deletions

diff --git a/tmk_core/common/sync_timer.c b/tmk_core/common/sync_timer.c
index de24b463b..68b92d8b4 100644
--- a/tmk_core/common/sync_timer.c
+++ b/tmk_core/common/sync_timer.c
@@ -26,7 +26,7 @@ SOFTWARE.
 #include "sync_timer.h"
 #include "keyboard.h"
 
-#if defined(SPLIT_KEYBOARD) && !defined(DISABLE_SYNC_TIMER)
+#if (defined(SPLIT_KEYBOARD) || defined(SERIAL_LINK_ENABLE)) && !defined(DISABLE_SYNC_TIMER)
 volatile int32_t sync_timer_ms;
 
 void sync_timer_init(void) { sync_timer_ms = 0; }
diff --git a/tmk_core/common/sync_timer.h b/tmk_core/common/sync_timer.h
index 9ddef45bb..744e2b50d 100644
--- a/tmk_core/common/sync_timer.h
+++ b/tmk_core/common/sync_timer.h
@@ -32,7 +32,7 @@ SOFTWARE.
 extern "C" {
 #endif
 
-#if defined(SPLIT_KEYBOARD) && !defined(DISABLE_SYNC_TIMER)
+#if (defined(SPLIT_KEYBOARD) || defined(SERIAL_LINK_ENABLE)) && !defined(DISABLE_SYNC_TIMER)
 void     sync_timer_init(void);
 void     sync_timer_update(uint32_t time);
 uint16_t sync_timer_read(void);