diff --git a/demo/demo.c b/demo/demo.c
index 75d5cf8..a5ac674 100644
--- a/demo/demo.c
+++ b/demo/demo.c
@@ -1,3 +1,4 @@
+#include <string.h>
 #include <time.h>
 
 #ifdef IOWNANATHLON
diff --git a/tommath.h b/tommath.h
index 556b924..93fa74c 100644
--- a/tommath.h
+++ b/tommath.h
@@ -16,10 +16,8 @@
 #define BN_H_
 
 #include <stdio.h>
-#include <string.h>
 #include <stdlib.h>
 #include <stdint.h>
-#include <ctype.h>
 #include <limits.h>
 
 #include <tommath_class.h>
diff --git a/tommath_private.h b/tommath_private.h
index d154739..5d4ea63 100644
--- a/tommath_private.h
+++ b/tommath_private.h
@@ -16,6 +16,7 @@
 #define TOMMATH_PRIV_H_
 
 #include <tommath.h>
+#include <ctype.h>
 
 #ifdef __cplusplus
 extern "C" {