diff --git a/ruby/tests/generated_code.proto b/ruby/tests/generated_code.proto
index 3b934bd69..e8116697d 100644
--- a/ruby/tests/generated_code.proto
+++ b/ruby/tests/generated_code.proto
@@ -69,6 +69,11 @@ enum TestEnum {
   C = 3;
 }
 
+message testLowercaseNested {
+  message lowercase{}
+}
+
+
 message TestUnknown {
   TestUnknown optional_unknown = 11;
   repeated TestUnknown repeated_unknown = 31;
diff --git a/ruby/tests/generated_code_test.rb b/ruby/tests/generated_code_test.rb
index 6e6f915ad..aed1cf8eb 100644
--- a/ruby/tests/generated_code_test.rb
+++ b/ruby/tests/generated_code_test.rb
@@ -15,6 +15,8 @@ class GeneratedCodeTest < Test::Unit::TestCase
     # successfully creates message definitions and classes, not to test every
     # aspect of the extension (basic.rb is for that).
     A::B::C::TestMessage.new
+    A::B::C::TestMessage::NestedMessage.new
+    A::B::C::TestLowercaseNested::Lowercase.new
     FooBar::TestImportedMessage.new
     A::B::TestRubyPackageMessage.new
   end
diff --git a/src/google/protobuf/compiler/ruby/ruby_generator.cc b/src/google/protobuf/compiler/ruby/ruby_generator.cc
index 6b9ea8226..d6aa1f008 100644
--- a/src/google/protobuf/compiler/ruby/ruby_generator.cc
+++ b/src/google/protobuf/compiler/ruby/ruby_generator.cc
@@ -389,7 +389,7 @@ void GenerateMessageAssignment(
     "lookup(\"$full_name$\").msgclass\n",
     "full_name", message->full_name());
 
-  std::string nested_prefix = prefix + message->name() + "::";
+  std::string nested_prefix = prefix + RubifyConstant(message->name()) + "::";
   for (int i = 0; i < message->nested_type_count(); i++) {
     GenerateMessageAssignment(nested_prefix, message->nested_type(i), printer);
   }