diff --git a/Editor/Drawers/SerializableReferenceToAttributeDrawer.cs b/Editor/Drawers/SerializableReferenceToAttributeDrawer.cs
index 50fb71c..2a71359 100644
--- a/Editor/Drawers/SerializableReferenceToAttributeDrawer.cs
+++ b/Editor/Drawers/SerializableReferenceToAttributeDrawer.cs
@@ -1,4 +1,5 @@
-using System;
+#if UNITY_2019_3_OR_NEWER
+using System;
 using System.Reflection;
 using System.Runtime.Serialization;
 using Module.Inspector.Editor.Utilities;
@@ -151,4 +152,5 @@ namespace Module.Inspector.Editor
             return str.Replace('/', '+');
         }
     }
-}
\ No newline at end of file
+}
+#endif
\ No newline at end of file
diff --git a/Runtime/Drawers/SerializableReferenceToAttribute.cs b/Runtime/Drawers/SerializableReferenceToAttribute.cs
index 58fa73f..88ea13b 100644
--- a/Runtime/Drawers/SerializableReferenceToAttribute.cs
+++ b/Runtime/Drawers/SerializableReferenceToAttribute.cs
@@ -1,4 +1,5 @@
-using System;
+#if UNITY_2019_3_OR_NEWER
+using System;
 
 namespace Module.Inspector
 {
@@ -19,4 +20,5 @@ namespace Module.Inspector
             useType = true;
         }
     }
-}
\ No newline at end of file
+}
+#endif
\ No newline at end of file
diff --git a/package.json b/package.json
index 5b030d4..3172722 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "com.module.inspector",
-  "version": "1.3.1",
+  "version": "1.3.2",
   "displayName": "Module.Inspector",
   "description": "Custom inspector with various useful property drawers",
   "unity": "2019.2",