diff --git a/crypto/stack/stack.c b/crypto/stack/stack.c
index fbe9d6e75..331f90719 100644
--- a/crypto/stack/stack.c
+++ b/crypto/stack/stack.c
@@ -278,7 +278,7 @@ void sk_zero(_STACK *st)
         return;
     if (st->num <= 0)
         return;
-    memset((char *)st->data, 0, sizeof(st->data) * st->num);
+    memset((char *)st->data, 0, sizeof(*st->data) * st->num);
     st->num = 0;
 }