diff --git a/unittests/ADT/DenseSetTest.cpp b/unittests/ADT/DenseSetTest.cpp
new file mode 100644
index 0000000..7a35f52
--- /dev/null
+++ b/unittests/ADT/DenseSetTest.cpp
@@ -0,0 +1,30 @@
+//===- llvm/unittest/ADT/DenseSetTest.cpp - DenseSet unit tests --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "gtest/gtest.h"
+#include <llvm/ADT/DenseSet.h>
+
+using namespace llvm;
+
+namespace {
+
+// Test fixture
+class DenseSetTest : public testing::Test {
+};
+
+// Test hashing with a set of only two entries.
+TEST_F(DenseSetTest, DoubleEntrySetTest) {
+  llvm::DenseSet<unsigned> set(2);
+  set.insert(0);
+  set.insert(1);
+  // Original failure was an infinite loop in this call:
+  EXPECT_EQ(0, set.count(2));
+}
+
+}