diff --git a/elab_expr.cc b/elab_expr.cc
index 2c786ec99..1c93c7ce8 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -21,7 +21,7 @@
 # include  <typeinfo>
 # include  <cstdlib>
 # include  <cstring>
-# include  <limits.h>
+# include  <climits>
 # include "compiler.h"
 
 # include  "pform.h"
diff --git a/expr_synth.cc b/expr_synth.cc
index 4e506bacd..2845877c9 100644
--- a/expr_synth.cc
+++ b/expr_synth.cc
@@ -20,7 +20,7 @@
 # include "config.h"
 # include "compiler.h"
 
-# include  <stdlib.h>
+# include  <cstdlib>
 # include  <iostream>
 
 # include  "netlist.h"
diff --git a/netlist.cc b/netlist.cc
index 204121e7d..88bfeb384 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -23,6 +23,7 @@
 
 # include  <typeinfo>
 # include  <cstdlib>
+# include  <climits>
 # include  "compiler.h"
 # include  "netlist.h"
 # include  "netmisc.h"