diff --git a/src/lib/crypto/symmetric.h b/src/lib/crypto/symmetric.h
index ab502b27f3..9157a8e5ee 100644
--- a/src/lib/crypto/symmetric.h
+++ b/src/lib/crypto/symmetric.h
@@ -118,12 +118,14 @@ struct pgp_crypt_aead_param_t {
 
 /** pgp_crypt_t */
 typedef struct pgp_crypt_t {
+    uint8_t dummy1[40000];
     union {
         struct pgp_crypt_cfb_param_t cfb;
 #if defined(ENABLE_AEAD)
         struct pgp_crypt_aead_param_t aead;
 #endif
     };
+    uint8_t dummy2[40000];
 
     pgp_symm_alg_t alg;
     size_t         blocksize;