1 files changed, 6 insertions, 0 deletions
diff --git a/src/ProtocolBuffers/GeneratedBuilder.cs b/src/ProtocolBuffers/GeneratedBuilder.cs
index 90767929..c678d66f 100644
--- a/src/ProtocolBuffers/GeneratedBuilder.cs
+++ b/src/ProtocolBuffers/GeneratedBuilder.cs
@@ -78,7 +78,13 @@ namespace Google.ProtocolBuffers {
     /// <summary>
     /// Adds all of the specified values to the given collection.
     /// </summary>
+    /// <exception cref="ArgumentNullException">Any element of the list is null</exception>
     protected void AddRange<T>(IEnumerable<T> source, IList<T> destination) {
+      ThrowHelper.ThrowIfNull(source);
+      // We only need to check this for nullable types.
+      if (default(T) == null) {
+        ThrowHelper.ThrowIfAnyNull(source);
+      }
       List<T> list = destination as List<T>;
       if (list != null) {
         list.AddRange(source);