diff --git a/src/engine-gpgsm.c b/src/engine-gpgsm.c
index 07fde4a9..d20da655 100644
--- a/src/engine-gpgsm.c
+++ b/src/engine-gpgsm.c
@@ -1458,7 +1458,7 @@ gpgsm_encrypt (void *engine, gpgme_key_t recp[], const char *recpstring,
 
   if (!gpgsm)
     return gpg_error (GPG_ERR_INV_VALUE);
-  if (!recp)
+  if (!recp && !recpstring) /* Symmetric only */
     return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
 
   if ((flags & GPGME_ENCRYPT_NO_ENCRYPT_TO))