diff --git a/BaseTools/Tests/RunTests.py b/BaseTools/Tests/RunTests.py
index e8ca2d055e..0dd65632d0 100644
--- a/BaseTools/Tests/RunTests.py
+++ b/BaseTools/Tests/RunTests.py
@@ -21,8 +21,6 @@ import unittest
 
 import TestTools
 
-sys.path.append(TestTools.PythonSourceDir)
-
 def GetCTestSuite():
     import CToolsTests
     return CToolsTests.TheTestSuite()
diff --git a/BaseTools/Tests/TestTools.py b/BaseTools/Tests/TestTools.py
index ac009db1fa..27afd79f20 100644
--- a/BaseTools/Tests/TestTools.py
+++ b/BaseTools/Tests/TestTools.py
@@ -1,7 +1,7 @@
 ## @file
 # Utility functions and classes for BaseTools unit tests
 #
-#  Copyright (c) 2008 - 2012, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2008 - 2015, Intel Corporation. All rights reserved.<BR>
 #
 #  This program and the accompanying materials
 #  are licensed and made available under the terms and conditions of the BSD License
@@ -31,6 +31,13 @@ CSourceDir = os.path.join(BaseToolsDir, 'Source', 'C')
 PythonSourceDir = os.path.join(BaseToolsDir, 'Source', 'Python')
 TestTempDir = os.path.join(TestsDir, 'TestTempDir')
 
+if PythonSourceDir not in sys.path:
+    #
+    # Allow unit tests to import BaseTools python modules. This is very useful
+    # for writing unit tests.
+    #
+    sys.path.append(PythonSourceDir)
+
 def MakeTheTestSuite(localItems):
     tests = []
     for name, item in localItems.iteritems():