diff --git a/arch/c5471/include/limits.h b/arch/c5471/include/limits.h
index 554c9f1f17..a692c9c36f 100644
--- a/arch/c5471/include/limits.h
+++ b/arch/c5471/include/limits.h
@@ -44,6 +44,7 @@
  * Definitions
  ************************************************************/
 
+#define CHAR_BIT        8
 #define SCHAR_MIN	0x80
 #define SCHAR_MAX	0x7f
 #define UCHAR_MAX	0xff
diff --git a/arch/dm320/include/limits.h b/arch/dm320/include/limits.h
index 554c9f1f17..a692c9c36f 100644
--- a/arch/dm320/include/limits.h
+++ b/arch/dm320/include/limits.h
@@ -44,6 +44,7 @@
  * Definitions
  ************************************************************/
 
+#define CHAR_BIT        8
 #define SCHAR_MIN	0x80
 #define SCHAR_MAX	0x7f
 #define UCHAR_MAX	0xff
diff --git a/arch/pjrc-8051/include/limits.h b/arch/pjrc-8051/include/limits.h
index c0b91e63dc..a6bffc0ed9 100644
--- a/arch/pjrc-8051/include/limits.h
+++ b/arch/pjrc-8051/include/limits.h
@@ -44,6 +44,7 @@
  * Definitions
  ************************************************************/
 
+#define CHAR_BIT        8
 #define SCHAR_MIN	0x80
 #define SCHAR_MAX	0x7f
 #define UCHAR_MAX	0xff
diff --git a/arch/sim/include/limits.h b/arch/sim/include/limits.h
index 554c9f1f17..a692c9c36f 100644
--- a/arch/sim/include/limits.h
+++ b/arch/sim/include/limits.h
@@ -44,6 +44,7 @@
  * Definitions
  ************************************************************/
 
+#define CHAR_BIT        8
 #define SCHAR_MIN	0x80
 #define SCHAR_MAX	0x7f
 #define UCHAR_MAX	0xff