diff --git a/src/modules/simulator/simulator_mavlink.cpp b/src/modules/simulator/simulator_mavlink.cpp
index a10c89792d..c2f7aa2f47 100644
--- a/src/modules/simulator/simulator_mavlink.cpp
+++ b/src/modules/simulator/simulator_mavlink.cpp
@@ -39,6 +39,10 @@
 #include <drivers/drv_pwm_output.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
+#ifdef __PX4_LINUX
+#define _GNU_SOURCE
+#endif
+#include <pthread.h>
 
 extern "C" __EXPORT hrt_abstime hrt_reset(void);