diff --git a/crypto/stack/stack.c b/crypto/stack/stack.c
index 1b89f551f1559e4e05940ecf5bb667269285ad10..7d97c2cbb41c29022960a6b36db2a33e83e03646 100644
--- a/crypto/stack/stack.c
+++ b/crypto/stack/stack.c
@@ -299,7 +299,7 @@ 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;
 }