diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -727,9 +727,9 @@
             exe_in_cwd = os.path.join(cmd_shenv.cwd, args[0])
             if os.path.isfile(exe_in_cwd):
                 executable = exe_in_cwd
-        if not executable:
+        if executable is None:
             executable = lit.util.which(args[0], cmd_shenv.env['PATH'])
-        if not executable:
+        if executable is None:
             raise InternalShellError(j, '%r: command not found' % args[0])
 
         # Replace uses of /dev/null with temporary files.