diff --git a/ext/extconf.rb b/ext/extconf.rb
index 1961f66..a692423 100644
--- a/ext/extconf.rb
+++ b/ext/extconf.rb
@@ -38,7 +38,7 @@ def crash(str)
   ["lua", "lua5.1", "lua5.2"].any? do |l|
     ldf = `#{ex} --libs #{l}`.chomp
     cf = `#{ex} --cflags #{l}`.chomp
-    next false if ldf.empty? or cf.empty?
+    next false if ldf.empty? and cf.empty?
 
     $LDFLAGS << " #{ldf}"
     $CFLAGS  << " #{cf}"