diff --git a/lib/auxlib.h b/lib/auxlib.h
index a57ffe01a..7610fac9f 100644
--- a/lib/auxlib.h
+++ b/lib/auxlib.h
@@ -9,6 +9,8 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <sys/resource.h>
+#include <unistd.h>
+#include <sys/syscall.h>
 
 
 #define THREAD_BUF_SIZE		64
@@ -436,6 +438,12 @@ INLINE int rlim(int res, rlim_t val) {
 	return setrlimit(res, &rlim);
 }
 
+#if defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 30))
+INLINE pid_t gettid(void) {
+	return syscall(SYS_gettid);
+}
+#endif
+
 
 
 /*** TAINT FUNCTIONS ***/