diff --git a/converter/src/main/java/tech/allegro/schema/json2avro/converter/JsonGenericRecordReader.java b/converter/src/main/java/tech/allegro/schema/json2avro/converter/JsonGenericRecordReader.java
index 76ae90f..2d86dbc 100644
--- a/converter/src/main/java/tech/allegro/schema/json2avro/converter/JsonGenericRecordReader.java
+++ b/converter/src/main/java/tech/allegro/schema/json2avro/converter/JsonGenericRecordReader.java
@@ -61,24 +61,31 @@ public GenericData.Record read(Map<String, Object> json, Schema schema) {
         }
     }
 
-    private GenericData.Record readRecord(Map<String, Object> json, Schema schema, Deque<String> path) {
-        final GenericRecordBuilder record = new GenericRecordBuilder(schema);
-        final Map<String,Field> fieldAliasMap = new HashMap<>(1);
+    private static Map<String, Field> getFieldAliasMap(final Schema schema) {
+        final Map<String, Field> fieldAliasMap = new HashMap<>(1);
         for (Field field: schema.getFields()) {
             for (String alias: field.aliases()) {
                 fieldAliasMap.put(alias, field);
             }
         }
+        return fieldAliasMap;
+    }
+
+    private GenericData.Record readRecord(Map<String, Object> json, Schema schema, Deque<String> path) {
+        final GenericRecordBuilder record = new GenericRecordBuilder(schema);
         json.entrySet().forEach(entry -> {
             final String entryKey = entry.getKey();
             final Field field = schema.getField(entryKey);
             if (field != null) {
                 record.set(field, read(field, field.schema(), entry.getValue(), path, false));
-            } else if (fieldAliasMap.containsKey(entryKey)) {
-                final Field aliasedField = fieldAliasMap.get(entryKey);
-                record.set(aliasedField, read(aliasedField, aliasedField.schema(), entry.getValue(), path, false));
-            } else if (unknownFieldListener != null) {
-                unknownFieldListener.onUnknownField(entry.getKey(), entry.getValue(), PathsPrinter.print(path, entry.getKey()));
+            } else {
+                final Map<String, Field> fieldAliasMap = getFieldAliasMap(schema);
+                if (fieldAliasMap.containsKey(entryKey)) {
+                    final Field aliasedField = fieldAliasMap.get(entryKey);
+                    record.set(aliasedField, read(aliasedField, aliasedField.schema(), entry.getValue(), path, false));
+                } else if (unknownFieldListener != null) {
+                    unknownFieldListener.onUnknownField(entry.getKey(), entry.getValue(), PathsPrinter.print(path, entry.getKey()));
+                }
             }
         });
         return record.build();