diff --git a/src/libcharon/encoding/message.c b/src/libcharon/encoding/message.c
index aa774e0c3..17adc5eb9 100644
--- a/src/libcharon/encoding/message.c
+++ b/src/libcharon/encoding/message.c
@@ -1419,8 +1419,8 @@ METHOD(message_t, generate, status_t,
 			chunk_free(&hash);
 		}
 
-		/* if at least one payload requires encryption, encrypt the message */
-		/* TODO-IKEV1: set is_encrypted externally instead of this check? */
+		/* if at least one payload requires encryption, encrypt the message.
+		 * if we have no key material available, the flag will be reset below */
 		enumerator = this->payloads->create_enumerator(this->payloads);
 		while (enumerator->enumerate(enumerator, (void**)&payload))
 		{
@@ -1447,6 +1447,7 @@ METHOD(message_t, generate, status_t,
 	else
 	{
 		DBG2(DBG_ENC, "not encrypting payloads");
+		this->is_encrypted = FALSE;
 	}
 
 	ike_header = ike_header_create_version(this->major_version,
diff --git a/src/libcharon/sa/keymat_v1.c b/src/libcharon/sa/keymat_v1.c
index 392032369..41a02cc86 100644
--- a/src/libcharon/sa/keymat_v1.c
+++ b/src/libcharon/sa/keymat_v1.c
@@ -759,6 +759,11 @@ METHOD(keymat_v1_t, get_hash_phase2, chunk_t,
 	bool add_message = TRUE;
 	char *name = "Hash";
 
+	if (!this->prf)
+	{	/* no keys derived yet */
+		return hash;
+	}
+
 	/* Hashes are simple for most exchanges in Phase 2:
 	 *   Hash = prf(SKEYID_a, M-ID | Complete message after HASH payload)
 	 * For Quick Mode there are three hashes: