1 files changed, 2 insertions, 2 deletions
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
index a5f6b7e8..c9dd6ea6 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
@@ -822,7 +822,7 @@ namespace Google.Protobuf.WellKnownTypes {
     public string Value {
       get { return value_; }
       set {
-        value_ = value ?? "";
+        value_ = pb::Preconditions.CheckNotNull(value, "value");
       }
     }
 
@@ -928,7 +928,7 @@ namespace Google.Protobuf.WellKnownTypes {
     public pb::ByteString Value {
       get { return value_; }
       set {
-        value_ = value ?? pb::ByteString.Empty;
+        value_ = pb::Preconditions.CheckNotNull(value, "value");
       }
     }