diff --git a/lib/fhir_models/bootstrap/hashable.rb b/lib/fhir_models/bootstrap/hashable.rb
index b124ec700..84171a145 100644
--- a/lib/fhir_models/bootstrap/hashable.rb
+++ b/lib/fhir_models/bootstrap/hashable.rb
@@ -51,7 +51,7 @@ def from_hash(hash)
         if !klass.nil? && !value.nil?
           # handle array of objects
           if value.is_a?(Array)
-            value.map! do |child|
+            value = value.map do |child|
               obj = child
               unless [FHIR::RESOURCES, FHIR::TYPES].flatten.include? child.class.name.gsub('FHIR::', '')
                 obj = make_child(child, klass)
@@ -68,7 +68,7 @@ def from_hash(hash)
           FHIR.logger.error("Unhandled and unrecognized class/type: #{meta['type']}")
         elsif value.is_a?(Array)
           # array of primitives
-          value.map! { |child| convert_primitive(child, meta) }
+          value = value.map { |child| convert_primitive(child, meta) }
           instance_variable_set("@#{local_name}", value)
         else
           # single primitive