diff --git a/src/io/ReadIO.hpp b/src/io/ReadIO.hpp
index c5bf5b90..72d90182 100644
--- a/src/io/ReadIO.hpp
+++ b/src/io/ReadIO.hpp
@@ -157,6 +157,29 @@ class DataBlock
   }
 };
 
+/// Helper struct to check if a StorageObjectType is allowed. Used in static
+/// assert.
+template<StorageObjectType T>
+struct is_allowed_storage_object_type : std::false_type
+{
+};
+
+/// Helper struct to check if a StorageObjectType is allowed. Used in static
+/// assert.
+template<>
+struct is_allowed_storage_object_type<StorageObjectType::Dataset>
+    : std::true_type
+{
+};
+
+/// Helper struct to check if a StorageObjectType is allowed. Used in static
+/// assert.
+template<>
+struct is_allowed_storage_object_type<StorageObjectType::Attribute>
+    : std::true_type
+{
+};
+
 /**
  * @brief Class for wrapping data objects (datasets or attributes) for reading
  * data from a file
@@ -182,29 +205,6 @@ class ReadDataWrapper
   {
   };
 
-  /// Helper struct to check if a StorageObjectType is allowed. Used in static
-  /// assert.
-  template<StorageObjectType T>
-  struct is_allowed_storage_object_type : std::false_type
-  {
-  };
-
-  /// Helper struct to check if a StorageObjectType is allowed. Used in static
-  /// assert.
-  template<>
-  struct is_allowed_storage_object_type<StorageObjectType::Dataset>
-      : std::true_type
-  {
-  };
-
-  /// Helper struct to check if a StorageObjectType is allowed. Used in static
-  /// assert.
-  template<>
-  struct is_allowed_storage_object_type<StorageObjectType::Attribute>
-      : std::true_type
-  {
-  };
-
   /**
    *  Static assert to enforce the restriction that ReadDataWrapper can only be
    *  instantiated for OTYPE of StorageObjectType::Dataset and