Index: llvm/trunk/utils/lit/lit/TestRunner.py
===================================================================
--- llvm/trunk/utils/lit/lit/TestRunner.py
+++ llvm/trunk/utils/lit/lit/TestRunner.py
@@ -238,7 +238,7 @@
 # args are from 'export' or 'env' command.
 # Returns copy of args without those commands or their arguments.
 def updateEnv(env, args):
-    arg_idx = 1
+    arg_idx_next = len(args)
     unset_next_env_var = False
     for arg_idx, arg in enumerate(args[1:]):
         # Support for the -u flag (unsetting) for env command
@@ -257,9 +257,10 @@
         key, eq, val = arg.partition('=')
         # Stop if there was no equals.
         if eq == '':
+            arg_idx_next = arg_idx + 1
             break
         env.env[key] = val
-    return args[arg_idx+1:]
+    return args[arg_idx_next:]
 
 def executeBuiltinEcho(cmd, shenv):
     """Interpret a redirected echo command"""
@@ -880,6 +881,9 @@
             #   env FOO=1 llc < %s | env BAR=2 llvm-mc | FileCheck %s
             cmd_shenv = ShellEnvironment(shenv.cwd, shenv.env)
             args = updateEnv(cmd_shenv, j.args)
+            if not args:
+                raise InternalShellError(j,
+                                         "Error: 'env' requires a subcommand")
 
         stdin, stdout, stderr = processRedirects(j, default_stdin, cmd_shenv,
                                                  opened_files)
Index: llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-assign.txt
===================================================================
--- llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-assign.txt
+++ llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-assign.txt
@@ -0,0 +1 @@
+# RUN: env FOO=1
Index: llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u-arg.txt
===================================================================
--- llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u-arg.txt
+++ llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u-arg.txt
@@ -0,0 +1 @@
+# RUN: env -u FOO
Index: llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u.txt
===================================================================
--- llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u.txt
+++ llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-last-is-u.txt
@@ -0,0 +1 @@
+# RUN: env -u
Index: llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-none.txt
===================================================================
--- llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-none.txt
+++ llvm/trunk/utils/lit/tests/Inputs/shtest-env/env-args-none.txt
@@ -0,0 +1 @@
+# RUN: env
Index: llvm/trunk/utils/lit/tests/shtest-env.py
===================================================================
--- llvm/trunk/utils/lit/tests/shtest-env.py
+++ llvm/trunk/utils/lit/tests/shtest-env.py
@@ -1,12 +1,30 @@
 # Check the env command
 #
-# RUN: %{lit} -j 1 -a -v %{inputs}/shtest-env \
+# RUN: not %{lit} -j 1 -a -v %{inputs}/shtest-env \
 # RUN: | FileCheck -match-full-lines %s
 #
 # END.
 
 # Make sure env commands are included in printed commands.
 
+# CHECK: -- Testing: 7 tests{{.*}}
+
+# CHECK: FAIL: shtest-env :: env-args-last-is-assign.txt ({{[^)]*}})
+# CHECK: Error: 'env' requires a subcommand
+# CHECK: error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-args-last-is-u-arg.txt ({{[^)]*}})
+# CHECK: Error: 'env' requires a subcommand
+# CHECK: error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-args-last-is-u.txt ({{[^)]*}})
+# CHECK: Error: 'env' requires a subcommand
+# CHECK: error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-args-none.txt ({{[^)]*}})
+# CHECK: Error: 'env' requires a subcommand
+# CHECK: error: command failed with exit status: {{.*}}
+
 # CHECK: PASS: shtest-env :: env-u.txt ({{[^)]*}})
 # CHECK: $ "{{[^"]*}}" "print_environment.py"
 # CHECK: $ "env" "-u" "FOO" "{{[^"]*}}" "print_environment.py"
@@ -21,3 +39,5 @@
 # CHECK: $ "env" "A_FOO=1" "-u" "FOO" "B_BAR=2" "-u" "BAR" "C_OOF=3" "{{[^"]*}}" "print_environment.py"
 
 # CHECK: Expected Passes : 3
+# CHECK: Unexpected Failures: 4
+# CHECK-NOT: {{.}}