diff --git a/elab_expr.cc b/elab_expr.cc
index e345d3ea4..11ac12dcc 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -21,6 +21,7 @@
 # include  <typeinfo>
 # include  <cstdlib>
 # include  <cstring>
+# include  <limits.h>
 # include "compiler.h"
 
 # include  "pform.h"
diff --git a/expr_synth.cc b/expr_synth.cc
index 49ab9b306..d323b7dd3 100644
--- a/expr_synth.cc
+++ b/expr_synth.cc
@@ -20,6 +20,7 @@
 # include "config.h"
 # include "compiler.h"
 
+# include  <stdlib.h>
 # include  <iostream>
 
 # include  "netlist.h"
diff --git a/tgt-null/null.c b/tgt-null/null.c
index 516c3cd37..9bed4a68d 100644
--- a/tgt-null/null.c
+++ b/tgt-null/null.c
@@ -18,6 +18,7 @@
  */
 
 # include "config.h"
+# include  <string.h>
 
 /*
  * This is a null target module. It does nothing.