diff --git a/src/c/symbols_list.h b/src/c/symbols_list.h
index ff77ac41c..9cfe677cf 100644
--- a/src/c/symbols_list.h
+++ b/src/c/symbols_list.h
@@ -1238,6 +1238,7 @@ cl_symbols[] = {
 {SYS_ "MKDIR" ECL_FUN("si_mkdir", si_mkdir, 2) ECL_VAR(SI_ORDINARY, OBJNULL)},
 {EXT_ "MKSTEMP" ECL_FUN("si_mkstemp", si_mkstemp, 1) ECL_VAR(EXT_ORDINARY, OBJNULL)},
 {SYS_ "NEED-TO-MAKE-LOAD-FORM-P" ECL_FUN("si_need_to_make_load_form_p", si_need_to_make_load_form_p, 1) ECL_VAR(SI_ORDINARY, OBJNULL)},
+{SYS_ "RADIX" ECL_FUN(NULL, NULL, -1) ECL_VAR(SI_ORDINARY, OBJNULL)},
 {SYS_ "RMDIR" ECL_FUN("si_rmdir", si_rmdir, 1) ECL_VAR(SI_ORDINARY, OBJNULL)},
 {EXT_ "MAKE-PIPE" ECL_FUN("si_make_pipe", si_make_pipe, 0) ECL_VAR(EXT_ORDINARY, OBJNULL)},
 /* package extensions */
diff --git a/src/lsp/predlib.lsp b/src/lsp/predlib.lsp
index ac2b2c550..85094ff5f 100644
--- a/src/lsp/predlib.lsp
+++ b/src/lsp/predlib.lsp
@@ -130,10 +130,15 @@ retrieved by (documentation 'NAME 'type)."
 (deftype index ()
   '(INTEGER 0 #.array-dimension-limit))
 
+(deftype radix ()
+  "A RADIX is an integer between 2 and 36, that is supported integer base."
+  '(INTEGER 2 36))
+
 (deftype fixnum ()
   "A FIXNUM is an integer between MOST-NEGATIVE-FIXNUM and
 MOST-POSITIVE-FIXNUM inclusive.  Other integers are bignums."
   '(INTEGER #.most-negative-fixnum #.most-positive-fixnum))
+
 (deftype bignum ()
   '(OR (INTEGER * (#.most-negative-fixnum)) (INTEGER (#.most-positive-fixnum) *)))