diff --git a/src/util/approx_nat.h b/src/util/approx_nat.h
index be5fc4fb6..354ead92b 100644
--- a/src/util/approx_nat.h
+++ b/src/util/approx_nat.h
@@ -21,7 +21,7 @@ Notes:
 #define APPROX_NAT_H_
 
 #include<iostream>
-#include<limits>
+#include<climits>
 
 class approx_nat {
     unsigned m_value;