diff --git a/src/simpgmspace.h b/src/simpgmspace.h
index 407dfc4a7..f96a0dd3b 100644
--- a/src/simpgmspace.h
+++ b/src/simpgmspace.h
@@ -388,7 +388,9 @@ inline void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct) {
 
 #define configure_pins(...)
 
+extern "C" {
 extern char simuSdDirectory[1024];
+}
 #define sdMountPoll()
 #define sdPoll10ms()
 #define sd_card_ready()  (true)