diff --git a/tool/fake.rb b/tool/fake.rb
index d7460e2f85..06f730288a 100644
--- a/tool/fake.rb
+++ b/tool/fake.rb
@@ -6,7 +6,7 @@ class File
   end
 end
 
-static = !!$static
+static = !!(defined?($static) && $static)
 $:.unshift(builddir)
 posthook = proc do
   config = RbConfig::CONFIG