diff --git a/targets/RT/USER/lte-softmodem.c b/targets/RT/USER/lte-softmodem.c
index 3002370ad9..a1001fa598 100644
--- a/targets/RT/USER/lte-softmodem.c
+++ b/targets/RT/USER/lte-softmodem.c
@@ -31,6 +31,9 @@
  */
 
 
+#define _GNU_SOURCE             /* See feature_test_macros(7) */
+#include <sched.h>
+
 
 #include "T.h"