diff --git a/src/main/target/SITL/target.c b/src/main/target/SITL/target.c
index bc13b9aef3..976056f112 100644
--- a/src/main/target/SITL/target.c
+++ b/src/main/target/SITL/target.c
@@ -55,6 +55,8 @@ const timerHardware_t timerHardware[1]; // unused
 #include "dyad.h"
 #include "target/SITL/udplink.h"
 
+uint32_t SystemCoreClock;
+
 static fdm_packet fdmPkt;
 static servo_packet pwmPkt;
 
diff --git a/src/main/target/SITL/target.h b/src/main/target/SITL/target.h
index 20cc9b569e..035b71dbb2 100644
--- a/src/main/target/SITL/target.h
+++ b/src/main/target/SITL/target.h
@@ -144,7 +144,7 @@
 
 // belows are internal stuff
 
-uint32_t SystemCoreClock;
+extern uint32_t SystemCoreClock;
 
 #ifdef EEPROM_IN_RAM
 extern uint8_t eepromData[EEPROM_SIZE];