diff --git a/tmk_core/common/action_util.c b/tmk_core/common/action_util.c
index 7f948b3a580..996a56c2e47 100644
--- a/tmk_core/common/action_util.c
+++ b/tmk_core/common/action_util.c
@@ -62,12 +62,12 @@ void oneshot_locked_mods_set_kb(uint8_t mods) {
 /** \brief Callback which is called when the one shot modifiers have been locked.
  */
 __attribute__((weak))
-void oneshot_locked_mods_cleared_user() { }
+void oneshot_locked_mods_cleared_user(void) { }
 
 /** \brief Callback which is called when the locked one shot modifiers have been locked.
  */
 __attribute__((weak))
-void oneshot_locked_mods_cleared_kb() {
+void oneshot_locked_mods_cleared_kb(void) {
     oneshot_locked_mods_cleared_user();
 }
 
@@ -79,7 +79,7 @@ void oneshot_mods_set_user(uint8_t mods) { }
 /** \brief Callback which is called when the one shot modifiers have been cleared.
  */
 __attribute__((weak))
-void oneshot_mods_cleared_user() { }
+void oneshot_mods_cleared_user(void) { }
 
 /** \brief Callback which is called when the one shot modifiers have been set.
  */
diff --git a/tmk_core/common/action_util.h b/tmk_core/common/action_util.h
index 2ac99ff7486..c2f7f588e9c 100644
--- a/tmk_core/common/action_util.h
+++ b/tmk_core/common/action_util.h
@@ -30,12 +30,12 @@ void send_keyboard_report(void);
 
 void oneshot_locked_mods_set_user(uint8_t mods);
 void oneshot_locked_mods_set_kb(uint8_t mods);
-void oneshot_locked_mods_cleared_user();
-void oneshot_locked_mods_cleared_kb();
+void oneshot_locked_mods_cleared_user(void);
+void oneshot_locked_mods_cleared_kb(void);
 void oneshot_mods_set_user(uint8_t mods);
 void oneshot_mods_set_kb(uint8_t mods);
-void oneshot_mods_cleared_user();
-void oneshot_mods_cleared_kb();
+void oneshot_mods_cleared_user(void);
+void oneshot_mods_cleared_kb(void);
 
 /* key */
 inline void add_key(uint8_t key) {