diff --git a/src/google/protobuf/compiler/ruby/ruby_generator_unittest.cc b/src/google/protobuf/compiler/ruby/ruby_generator_unittest.cc
index 6c203ab..1b04cb3 100644
--- a/src/google/protobuf/compiler/ruby/ruby_generator_unittest.cc
+++ b/src/google/protobuf/compiler/ruby/ruby_generator_unittest.cc
@@ -47,6 +47,7 @@
 
 string FindRubyTestDir(const string& file) {
   // Inspired by TestSourceDir() in src/google/protobuf/testing/googletest.cc.
+#ifndef GOOGLE_THIRD_PARTY_PROTOBUF
   string prefix = ".";
   while (!File::Exists(prefix + "/src/google/protobuf/compiler/ruby" + file)) {
     if (!File::Exists(prefix)) {
@@ -57,6 +58,9 @@
     prefix += "/..";
   }
   return prefix + "/src/google/protobuf/compiler/ruby";
+#else
+  return "third_party/protobuf/src/google/protobuf/compiler/ruby";
+#endif  // GOOGLE_THIRD_PARTY_PROTOBUF
 }
 
 // This test is a simple golden-file test over the output of the Ruby code