diff --git a/src/dungeon.c b/src/dungeon.c
index 1f0c56519..07cd2f56b 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -1484,6 +1484,7 @@ stairway_add(coordxy x, coordxy y, boolean up, boolean isladder, d_level *dest)
 {
     stairway *tmp = (stairway *) alloc(sizeof (stairway));
 
+    (void) memset((genericptr_t) tmp, 0, sizeof (stairway));
     tmp->sx = x;
     tmp->sy = y;
     tmp->up = up;
diff --git a/src/mklev.c b/src/mklev.c
index 388591db7..3de0635e4 100644
--- a/src/mklev.c
+++ b/src/mklev.c
@@ -458,6 +458,8 @@ alloc_doors(void)
     if (!gd.doors || gd.doorindex >= gd.doors_alloc) {
         int c = gd.doors_alloc + DOORINC;
         coord *doortmp = (coord *) alloc(c * sizeof(coord));
+
+        (void) memset((genericptr_t) doortmp, 0, c * sizeof(coord));
         if (gd.doors) {
             (void) memcpy(doortmp, gd.doors, gd.doors_alloc * sizeof(coord));
             free(gd.doors);