1 files changed, 12 insertions, 0 deletions
diff --git a/csharp/src/Google.Protobuf/MessageParser.cs b/csharp/src/Google.Protobuf/MessageParser.cs
index 4d35554a..d3fa6cb1 100644
--- a/csharp/src/Google.Protobuf/MessageParser.cs
+++ b/csharp/src/Google.Protobuf/MessageParser.cs
@@ -69,6 +69,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             message.MergeFrom(data, DiscardUnknownFields);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -83,6 +84,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             message.MergeFrom(data, offset, length, DiscardUnknownFields);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -95,6 +97,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             message.MergeFrom(data, DiscardUnknownFields);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -107,6 +110,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             message.MergeFrom(input, DiscardUnknownFields);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -123,6 +127,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             message.MergeDelimitedFrom(input, DiscardUnknownFields);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -135,6 +140,7 @@ namespace Google.Protobuf
         {
             IMessage message = factory();
             MergeFrom(message, input);
+            CheckMergedRequiredFields(message);
             return message;
         }
 
@@ -167,6 +173,12 @@ namespace Google.Protobuf
             }
         }
 
+        internal static void CheckMergedRequiredFields(IMessage message)
+        {
+            if (!message.IsInitialized())
+                throw new InvalidOperationException("Parsed message does not contain all required fields");
+        }
+
         /// <summary>
         /// Creates a new message parser which optionally discards unknown fields when parsing.
         /// </summary>