diff --git a/llvm/utils/lit/tests/lit.cfg b/llvm/utils/lit/tests/lit.cfg
--- a/llvm/utils/lit/tests/lit.cfg
+++ b/llvm/utils/lit/tests/lit.cfg
@@ -35,6 +35,13 @@
 else:
   lit_path = os.path.join(config.test_source_root, '..')
 
+# This test suite calls %{lit} to test lit's behavior for the sample test
+# suites in %{inputs}.  This test suite's results are then determined in part
+# by %{lit}'s textual output, which includes the output of FileCheck calls
+# within %{inputs}'s test suites.  Thus, %{lit} clears environment variables
+# that can affect FileCheck's output.
+llvm_config.clear_environment(['FILECHECK_OPTS', 'FILECHECK_DUMP_INPUT_ON_FAILURE'])
+
 # Required because some tests import the lit module
 llvm_config.with_environment('PYTHONPATH', lit_path, append_path=True)
 
@@ -44,16 +51,10 @@
     if directory:
         llvm_config.with_environment('PATH', directory, append_path=True)
 
-# This test suite calls %{lit} to test lit's behavior for the sample test
-# suites in %{inputs}.  This test suite's results are then determined in part
-# by %{lit}'s textual output, which includes the output of FileCheck calls
-# within %{inputs}'s test suites.  Thus, %{lit} clears environment variables
-# that can affect FileCheck's output.
 config.substitutions.append(('%{inputs}', os.path.join(
     config.test_source_root, 'Inputs')))
 config.substitutions.append(('%{lit}',
-    "{env} %{{python}} {lit}".format(
-        env="env FILECHECK_OPTS= FILECHECK_DUMP_INPUT_ON_FAILURE=",
+    "%{{python}} {lit}".format(
         lit=os.path.join(lit_path, 'lit.py'))))
 config.substitutions.append(('%{python}', '"%s"' % (sys.executable)))