diff --git a/targets/RT/USER/lte-ue.c b/targets/RT/USER/lte-ue.c
index 6c4504ecf5..729623602c 100644
--- a/targets/RT/USER/lte-ue.c
+++ b/targets/RT/USER/lte-ue.c
@@ -972,7 +972,7 @@ void ue_stub_rx_handler(unsigned int num_bytes,
   }
 }
 
-uint64_t clock_usec()
+uint64_t clock_usec(void)
 {
     struct timespec t;
     if (clock_gettime(CLOCK_MONOTONIC, &t) == -1)