diff --git a/configure.py b/configure.py
--- a/configure.py
+++ b/configure.py
@@ -40,18 +40,20 @@
 import mozpack.path as mozpath
 import six
 
 
 def main(argv):
-    _activate_build_virtualenv()
     config = {}
 
     if "OLD_CONFIGURE" not in os.environ:
         os.environ["OLD_CONFIGURE"] = os.path.join(base_dir, "old-configure")
 
     sandbox = ConfigureSandbox(config, os.environ, argv)
 
+    if not sandbox._help:
+        _activate_build_virtualenv()
+
     clobber_file = "CLOBBER"
     if not os.path.exists(clobber_file):
         # Simply touch the file.
         with open(clobber_file, "a"):
             pass