diff --git a/OmopTransformer/Documentation/JSONRendering/JSONStructure.cs b/OmopTransformer/Documentation/JSONRendering/JSONStructure.cs
index de5af5f..3642657 100644
--- a/OmopTransformer/Documentation/JSONRendering/JSONStructure.cs
+++ b/OmopTransformer/Documentation/JSONRendering/JSONStructure.cs
@@ -2,7 +2,7 @@
 
 public class JSONStructure
 {
-    public string OmopTable { get; set; }
-    public string Origin { get; set; }
-    public List<OMOPColumns> OmopColumns { get; set; }
+    public string OmopTable { get; set; } = string.Empty;
+    public string Origin { get; set; } = string.Empty;
+    public List<OMOPColumns> OmopColumns { get; set; } = [];
 }
\ No newline at end of file
diff --git a/OmopTransformer/Documentation/JSONRendering/OMOPColumns.cs b/OmopTransformer/Documentation/JSONRendering/OMOPColumns.cs
index da323a5..1cb85bc 100644
--- a/OmopTransformer/Documentation/JSONRendering/OMOPColumns.cs
+++ b/OmopTransformer/Documentation/JSONRendering/OMOPColumns.cs
@@ -2,6 +2,6 @@
 
 public class OMOPColumns
 {
-    public string Name { get; set; }
-    public List<string> SourceColumns { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public List<string> SourceColumns { get; set; } = [];
 }
\ No newline at end of file