diff --git a/sim/ppc/hw_sem.c b/sim/ppc/hw_sem.c
index c43af3b1d9e..9495b8591b9 100644
--- a/sim/ppc/hw_sem.c
+++ b/sim/ppc/hw_sem.c
@@ -111,7 +111,7 @@ hw_sem_init_data(device *me)
   hw_sem_device *sem = (hw_sem_device*)device_data(me);
   const device_unit *d;
   int status;
-  union semun help;
+  union semun help = {};
 
   /* initialize the properties of the sem */
 
@@ -190,7 +190,7 @@ hw_sem_io_read_buffer(device *me,
   struct sembuf sb;
   int status;
   uint32_t u32;
-  union semun help;
+  union semun help = {};
 
   /* do we need to worry about out of range addresses? */