diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index a74feabf06f3..e862889f2636 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -2686,6 +2686,11 @@ static void clang_parseTranslationUnit_Impl(void *UserData) {
   unsigned options = PTUI->options;
   CXTranslationUnit *out_TU = PTUI->out_TU;
 
+  // Set up the initial return values.
+  if (out_TU)
+    *out_TU = NULL;
+  PTUI->result = CXError_Failure;
+
   // Check arguments.
   if (!CIdx || !out_TU ||
       (unsaved_files == NULL && num_unsaved_files != 0)) {
@@ -2693,10 +2698,6 @@ static void clang_parseTranslationUnit_Impl(void *UserData) {
     return;
   }
 
-  // Set up the initial return values.
-  *out_TU = NULL;
-  PTUI->result = CXError_Failure;
-
   CIndexer *CXXIdx = static_cast<CIndexer *>(CIdx);
 
   if (CXXIdx->isOptEnabled(CXGlobalOpt_ThreadBackgroundPriorityForIndexing))
@@ -2826,12 +2827,8 @@ clang_parseTranslationUnit(CXIndex CIdx,
       CIdx, source_filename, command_line_args, num_command_line_args,
       unsaved_files, num_unsaved_files, options, &TU);
   (void)Result;
-
-  // FIXME: This probably papers over a problem. If the result is not success,
-  // no TU should be set.
-  if (Result != CXError_Success)
-    return 0;
-
+  assert((TU && Result == CXError_Success) ||
+         (!TU && Result != CXError_Success));
   return TU;
 }
 
diff --git a/clang/unittests/CMakeLists.txt b/clang/unittests/CMakeLists.txt
index f00008e04071..9cb08005403a 100644
--- a/clang/unittests/CMakeLists.txt
+++ b/clang/unittests/CMakeLists.txt
@@ -22,3 +22,4 @@ if(CLANG_ENABLE_REWRITER)
   add_subdirectory(Format)
   add_subdirectory(Sema)
 endif()
+add_subdirectory(libclang)
diff --git a/clang/unittests/Makefile b/clang/unittests/Makefile
index e4fbe584da1f..9b95a6eda20e 100644
--- a/clang/unittests/Makefile
+++ b/clang/unittests/Makefile
@@ -14,7 +14,7 @@ ifndef CLANG_LEVEL
 
 IS_UNITTEST_LEVEL := 1
 CLANG_LEVEL := ..
-PARALLEL_DIRS = Basic Lex Driver
+PARALLEL_DIRS = Basic Lex Driver libclang
 
 include $(CLANG_LEVEL)/../..//Makefile.config
 
diff --git a/clang/unittests/libclang/CMakeLists.txt b/clang/unittests/libclang/CMakeLists.txt
new file mode 100644
index 000000000000..1cdc45e2d22a
--- /dev/null
+++ b/clang/unittests/libclang/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_clang_unittest(libclangTests
+  LibclangTest.cpp
+  )
+
+target_link_libraries(libclangTests
+  libclang
+  )
diff --git a/clang/unittests/libclang/LibclangTest.cpp b/clang/unittests/libclang/LibclangTest.cpp
new file mode 100644
index 000000000000..7048af95842d
--- /dev/null
+++ b/clang/unittests/libclang/LibclangTest.cpp
@@ -0,0 +1,17 @@
+//===- unittests/libclang/LibclangTest.cpp --- libclang tests -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang-c/Index.h"
+#include "gtest/gtest.h"
+
+TEST(libclang, TestInvalidArgs) {
+  EXPECT_EQ(CXError_InvalidArguments,
+            clang_parseTranslationUnit2(0, 0, 0, 0, 0, 0, 0, 0));
+}
+
diff --git a/clang/unittests/libclang/Makefile b/clang/unittests/libclang/Makefile
new file mode 100644
index 000000000000..e96c925858e9
--- /dev/null
+++ b/clang/unittests/libclang/Makefile
@@ -0,0 +1,25 @@
+##===- unittests/libclang/Makefile -------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+CLANG_LEVEL = ../..
+TESTNAME = libclang
+include $(CLANG_LEVEL)/../../Makefile.config
+LINK_COMPONENTS := $(TARGETS_TO_BUILD) asmparser bitreader support mc option
+
+# Note that 'USEDLIBS' must include all of the core clang libraries
+# when -static is given to linker on cygming.
+USEDLIBS = clang.a \
+	   clangIndex.a clangFormat.a clangRewriteCore.a \
+	   clangFrontend.a clangDriver.a \
+	   clangTooling.a \
+	   clangSerialization.a clangParse.a clangSema.a \
+	   clangAnalysis.a clangEdit.a clangAST.a clangLex.a \
+	   clangBasic.a
+
+include $(CLANG_LEVEL)/unittests/Makefile