diff --git a/src/nnue/nnue_feature_transformer.h b/src/nnue/nnue_feature_transformer.h
index d2abd40fa..b9b422a65 100644
--- a/src/nnue/nnue_feature_transformer.h
+++ b/src/nnue/nnue_feature_transformer.h
@@ -194,6 +194,10 @@ fused(const typename VecWrapper::type& in, const T& operand, const Ts&... operan
         return fused<VecWrapper, ops...>(VecWrapper::add(in, operand), operands...);
     case Sub :
         return fused<VecWrapper, ops...>(VecWrapper::sub(in, operand), operands...);
+    default :
+        static_assert(update_op == Add || update_op == Sub,
+                      "Only Add and Sub are currently supported.");
+        return typename VecWrapper::type();
     }
 }