diff --git a/iguana/pb_reader.hpp b/iguana/pb_reader.hpp
index a91a6969..cfa4f6cf 100644
--- a/iguana/pb_reader.hpp
+++ b/iguana/pb_reader.hpp
@@ -72,15 +72,23 @@ IGUANA_INLINE void from_pb_impl(T& val, std::string_view& pb_str,
           throw std::invalid_argument(
               "Invalid fixed int value: too few bytes.");
         }
-      using item_type = typename T::value_type;
-      size_t start = pb_str.size();
+      if constexpr (is_fixed_v<item_type>) {
+        int num = size / sizeof(item_type);
+        int old_size = val.size();
+        detail::resize(val, old_size + num);
+        std::memcpy(val.data() + old_size, pb_str.data(), size);
+        pb_str = pb_str.substr(size);
+      }
+      else {
+        size_t start = pb_str.size();
 
-      while (!pb_str.empty()) {
-        item_type item;
-        from_pb_impl(item, pb_str);
-        val.push_back(std::move(item));
-        if (start - pb_str.size() == size) {
-          break;
+        while (!pb_str.empty()) {
+          item_type item;
+          from_pb_impl(item, pb_str);
+          val.push_back(std::move(item));
+          if (start - pb_str.size() == size) {
+            break;
+          }
         }
       }
     }