diff --git a/src/libstrongswan/crypto/iv/iv_gen_seq.c b/src/libstrongswan/crypto/iv/iv_gen_seq.c
index 70f1fce38..4de13744d 100644
--- a/src/libstrongswan/crypto/iv/iv_gen_seq.c
+++ b/src/libstrongswan/crypto/iv/iv_gen_seq.c
@@ -53,6 +53,10 @@ METHOD(iv_gen_t, get_iv, bool,
 	{
 		return FALSE;
 	}
+	if (size < sizeof(u_int64_t))
+	{
+		return FALSE;
+	}
 	if (this->prev != SEQ_IV_INIT_STATE && seq <= this->prev)
 	{
 		return FALSE;