diff --git a/src/c/array.d b/src/c/array.d
index e785dd7f4..ec4f4de24 100644
--- a/src/c/array.d
+++ b/src/c/array.d
@@ -16,6 +16,10 @@
 
 #include "ecls.h"
 
+#ifndef CHAR_BIT
+#define CHAR_BIT (sizeof(char)*8)
+#endif
+
 static void displace (cl_object from, cl_object to, cl_object offset);
 static void check_displaced (cl_object dlist, cl_object orig, cl_index newdim);
 extern enum aelttype get_aelttype (cl_object x);
diff --git a/src/c/cmpaux.d b/src/c/cmpaux.d
index 0aefeb787..34681d4f9 100644
--- a/src/c/cmpaux.d
+++ b/src/c/cmpaux.d
@@ -17,6 +17,10 @@
 #include "ecls.h"
 #include "ecls-inl.h"
 
+#ifndef CHAR_BIT
+#define CHAR_BIT (sizeof(char)*8)
+#endif
+
 cl_object @'&optional';
 cl_object @'&rest';
 cl_object @'&key';
diff --git a/src/c/read.d b/src/c/read.d
index 667e8888e..1ed0f6205 100644
--- a/src/c/read.d
+++ b/src/c/read.d
@@ -19,6 +19,10 @@
 #include "ecls-inl.h"
 #include <ctype.h>
 
+#ifndef CHAR_BIT
+#define CHAR_BIT (sizeof(char)*8)
+#endif
+
 /******************************* EXPORTS ******************************/
 
 cl_object standard_readtable;
diff --git a/src/c/sequence.d b/src/c/sequence.d
index 225f89901..d2f635b3b 100644
--- a/src/c/sequence.d
+++ b/src/c/sequence.d
@@ -17,6 +17,10 @@
 #include "ecls.h"
 #include "ecls-inl.h"
 
+#ifndef CHAR_BIT
+#define CHAR_BIT (sizeof(char)*8)
+#endif
+
 #undef endp
 
 #define	endp(obje)	(endp_temp = (obje), CONSP(endp_temp) ? \