diff --git a/csharp/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs b/csharp/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs
index 9abee95126..586ab47afd 100644
--- a/csharp/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs
+++ b/csharp/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs
@@ -71,7 +71,6 @@ namespace Google.Protobuf.Reflection
 
         private void TestFileDescriptor(FileDescriptor file, FileDescriptor importedFile, FileDescriptor importedPublicFile)
         {
-
             Assert.AreEqual("unittest_proto3.proto", file.Name);
             Assert.AreEqual("protobuf_unittest3", file.Package);
 
@@ -214,29 +213,61 @@ namespace Google.Protobuf.Reflection
         }
 
         [Test]
-        public void FieldDescriptor()
+        public void FieldDescriptor_GeneratedCode()
         {
-            MessageDescriptor messageType = TestAllTypes.Descriptor;
-            FieldDescriptor primitiveField = messageType.FindDescriptor<FieldDescriptor>("single_int32");
-            FieldDescriptor enumField = messageType.FindDescriptor<FieldDescriptor>("single_nested_enum");
-            FieldDescriptor messageField = messageType.FindDescriptor<FieldDescriptor>("single_foreign_message");
+            TestFieldDescriptor(UnittestProto3Reflection.Descriptor, TestAllTypes.Descriptor, ForeignMessage.Descriptor, ImportMessage.Descriptor);
+        }
+
+        [Test]
+        public void FieldDescriptor_BuildFromByteStrings()
+        {
+            // The descriptors have to be supplied in an order such that all the
+            // dependencies come before the descriptors depending on them.
+            var descriptorData = new List<ByteString>
+            {
+                UnittestImportPublicProto3Reflection.Descriptor.Proto.ToByteString(),
+                UnittestImportProto3Reflection.Descriptor.Proto.ToByteString(),
+                UnittestProto3Reflection.Descriptor.Proto.ToByteString()
+            };
+            var converted = FileDescriptor.BuildFromByteStrings(descriptorData);
+            TestFieldDescriptor(
+                converted[2],
+                converted[2].FindTypeByName<MessageDescriptor>("TestAllTypes"),
+                converted[2].FindTypeByName<MessageDescriptor>("ForeignMessage"),
+                converted[1].FindTypeByName<MessageDescriptor>("ImportMessage"));
+        }
+
+        public void TestFieldDescriptor(
+            FileDescriptor unitTestProto3Descriptor,
+            MessageDescriptor testAllTypesDescriptor,
+            MessageDescriptor foreignMessageDescriptor,
+            MessageDescriptor importMessageDescriptor)
+        {
+            FieldDescriptor primitiveField = testAllTypesDescriptor.FindDescriptor<FieldDescriptor>("single_int32");
+            FieldDescriptor enumField = testAllTypesDescriptor.FindDescriptor<FieldDescriptor>("single_nested_enum");
+            FieldDescriptor foreignMessageField = testAllTypesDescriptor.FindDescriptor<FieldDescriptor>("single_foreign_message");
+            FieldDescriptor importMessageField = testAllTypesDescriptor.FindDescriptor<FieldDescriptor>("single_import_message");
 
             Assert.AreEqual("single_int32", primitiveField.Name);
             Assert.AreEqual("protobuf_unittest3.TestAllTypes.single_int32",
                             primitiveField.FullName);
             Assert.AreEqual(1, primitiveField.FieldNumber);
-            Assert.AreEqual(messageType, primitiveField.ContainingType);
-            Assert.AreEqual(UnittestProto3Reflection.Descriptor, primitiveField.File);
+            Assert.AreEqual(testAllTypesDescriptor, primitiveField.ContainingType);
+            Assert.AreEqual(unitTestProto3Descriptor, primitiveField.File);
             Assert.AreEqual(FieldType.Int32, primitiveField.FieldType);
             Assert.IsNull(primitiveField.Proto.Options);
             
             Assert.AreEqual("single_nested_enum", enumField.Name);
             Assert.AreEqual(FieldType.Enum, enumField.FieldType);
-            Assert.AreEqual(messageType.EnumTypes[0], enumField.EnumType);
+            Assert.AreEqual(testAllTypesDescriptor.EnumTypes[0], enumField.EnumType);
+
+            Assert.AreEqual("single_foreign_message", foreignMessageField.Name);
+            Assert.AreEqual(FieldType.Message, foreignMessageField.FieldType);
+            Assert.AreEqual(foreignMessageDescriptor, foreignMessageField.MessageType);
 
-            Assert.AreEqual("single_foreign_message", messageField.Name);
-            Assert.AreEqual(FieldType.Message, messageField.FieldType);
-            Assert.AreEqual(ForeignMessage.Descriptor, messageField.MessageType);
+            Assert.AreEqual("single_import_message", importMessageField.Name);
+            Assert.AreEqual(FieldType.Message, importMessageField.FieldType);
+            Assert.AreEqual(importMessageDescriptor, importMessageField.MessageType);
         }
 
         [Test]
diff --git a/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs b/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
index 799f729106..216e03cc2d 100644
--- a/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
@@ -344,6 +344,7 @@ namespace Google.Protobuf.Reflection
                 FileDescriptor descriptor = new FileDescriptor(
                     data, proto, dependencies, pool,
                     allowUnknownDependencies: false, generatedCodeInfo: null);
+                descriptor.CrossLink();
                 descriptors.Add(descriptor);
                 if (descriptorsByName.ContainsKey(descriptor.Name))
                 {