diff --git a/arch/arm/src/stm32l4/stm32l4_rng.c b/arch/arm/src/stm32l4/stm32l4_rng.c
index 87bfaf98cd..a9dcf3ba54 100644
--- a/arch/arm/src/stm32l4/stm32l4_rng.c
+++ b/arch/arm/src/stm32l4/stm32l4_rng.c
@@ -302,7 +302,7 @@ static ssize_t stm32l4_rngread(struct file *filep, char *buffer, size_t buflen)
  * Public Functions
  ****************************************************************************/
 
-void up_rnginitialize()
+void up_rnginitialize(void)
 {
   stm32l4_rnginitialize();
   register_driver("/dev/random", &g_rngops, 0444, NULL);