diff --git a/sk2/calculator.h b/sk2/calculator.h
index 9bd1989..a17c318 100644
--- a/sk2/calculator.h
+++ b/sk2/calculator.h
@@ -1,5 +1,5 @@
 #ifndef CALCULATOR_H
-#defien CALCULATOR_H
+#define CALCULATOR_H
 
 
 /**