diff --git a/src/crypto/crypto.cpp b/src/crypto/crypto.cpp
index 45ecd954..266893d3 100644
--- a/src/crypto/crypto.cpp
+++ b/src/crypto/crypto.cpp
@@ -323,7 +323,7 @@ namespace Crypto {
   };
 
   static inline size_t rs_comm_size(size_t pubs_count) {
-    return sizeof(rs_comm) + pubs_count * sizeof(rs_comm().ab[0]);
+    return sizeof(rs_comm) + pubs_count * sizeof(((rs_comm*)0)->ab[0]);
   }
 
   void crypto_ops::generate_ring_signature(const Hash &prefix_hash, const KeyImage &image,