diff --git a/lldb/test/API/lit.cfg.py b/lldb/test/API/lit.cfg.py
--- a/lldb/test/API/lit.cfg.py
+++ b/lldb/test/API/lit.cfg.py
@@ -91,6 +91,13 @@
   This allows us to check if the attribute exists before trying to access it."""
   return getattr(config, attr, None)
 
+def is_configured_and_true(attr):
+  """Returns true if and only if the configuration attribute exists and it is
+  set to'1'.
+
+  This is useful when checking CMake variables that have been cannonicalized to
+  0/1."""
+  return getattr(config, attr, None) == '1'
 
 def delete_module_cache(path):
   """Clean the module caches in the test build directory.
@@ -171,7 +178,7 @@
   dotest_cmd += ['--env', 'LLVM_TOOLS_DIR=' + config.llvm_tools_dir]
 
 # If we have a just-built libcxx, prefer it over the system one.
-if is_configured('has_libcxx') and platform.system() != 'Windows':
+if is_configured_and_true('has_libcxx') and platform.system() != 'Windows':
   if is_configured('llvm_include_dir') and is_configured('llvm_libs_dir'):
     dotest_cmd += ['--libcxx-include-dir', os.path.join(config.llvm_include_dir, 'c++', 'v1')]
     dotest_cmd += ['--libcxx-library-dir', config.llvm_libs_dir]