diff --git a/contrib/20.r7rs/scheme/base.scm b/contrib/20.r7rs/scheme/base.scm
index 55385de1..7976fddc 100644
--- a/contrib/20.r7rs/scheme/base.scm
+++ b/contrib/20.r7rs/scheme/base.scm
@@ -9,7 +9,9 @@
                 ceiling
                 truncate
                 round
-                sqrt)
+                sqrt
+                nan?
+                infinite?)
           (picrin macro)
           (picrin string)
           (scheme file))
@@ -470,6 +472,16 @@
 
   ;; 6.2. Numbers
 
+  (define complex? number?)
+  (define real? number?)
+  (define rational? number?)
+  (define (integer? o)
+    (or (exact? o)
+        (and (inexact? o)
+             (not (nan? o))
+             (not (infinite? o))
+             (= o (floor o)))))
+
   (define (exact-integer? x)
     (and (exact? x)
          (integer? x)))
diff --git a/extlib/benz/number.c b/extlib/benz/number.c
index 35f0d921..5e8d6851 100644
--- a/extlib/benz/number.c
+++ b/extlib/benz/number.c
@@ -58,7 +58,7 @@ number_string(int val, int radix, int length, char *buffer) {
 }
 
 static pic_value
-pic_number_real_p(pic_state *pic)
+pic_number_number_p(pic_state *pic)
 {
   pic_value v;
 
@@ -71,32 +71,6 @@ pic_number_real_p(pic_state *pic)
 #endif
 }
 
-static pic_value
-pic_number_integer_p(pic_state *pic)
-{
-  pic_value v;
-
-  pic_get_args(pic, "o", &v);
-
-  if (pic_int_p(v)) {
-    return pic_true_value();
-  }
-#if PIC_ENABLE_FLOAT
-  if (pic_float_p(v)) {
-    double f = pic_float(v);
-
-    if (isinf(f)) {
-      return pic_false_value();
-    }
-
-    if (f == round(f)) {
-      return pic_true_value();
-    }
-  }
-#endif
-  return pic_false_value();
-}
-
 static pic_value
 pic_number_exact_p(pic_state *pic)
 {
@@ -451,11 +425,7 @@ pic_init_number(pic_state *pic)
 {
   size_t ai = pic_gc_arena_preserve(pic);
 
-  pic_defun(pic, "number?", pic_number_real_p);
-  pic_defun(pic, "complex?", pic_number_real_p);
-  pic_defun(pic, "real?", pic_number_real_p);
-  pic_defun(pic, "rational?", pic_number_real_p);
-  pic_defun(pic, "integer?", pic_number_integer_p);
+  pic_defun(pic, "number?", pic_number_number_p);
   pic_gc_arena_restore(pic, ai);
 
   pic_defun(pic, "exact?", pic_number_exact_p);