diff --git a/sources/NetArchTest/Dependencies/TypeCheckingContext.cs b/sources/NetArchTest/Dependencies/TypeCheckingContext.cs
index e3e4798..1afa979 100644
--- a/sources/NetArchTest/Dependencies/TypeCheckingContext.cs
+++ b/sources/NetArchTest/Dependencies/TypeCheckingContext.cs
@@ -105,7 +105,7 @@ private void CheckFields(TypeDefinition typeToCheck)
                 {
                     CheckCustomAttributes(field);
                     CheckTypeReference(field.FieldType);
-                    if (_serachForDependencyInFieldConstant && field.HasConstant && field.FieldType.FullName == typeof(string).FullName)
+                    if (_serachForDependencyInFieldConstant && field.HasConstant && field.FieldType.FullName == typeof(string).FullName && field.Constant != null)
                     {
                         _result.CheckType(field.Constant.ToString());
                     }