diff --git a/piclib/prelude.scm b/piclib/prelude.scm
index d7a191f5..2a9993cc 100644
--- a/piclib/prelude.scm
+++ b/piclib/prelude.scm
@@ -589,14 +589,6 @@
       s
       (fold f (f (car xs) s) (cdr xs))))
 
-;;; 6.3 Booleans
-
-(define (boolean=? . objs)
-  (or (every (lambda (x) (eq? x #t)) objs)
-      (every (lambda (x) (eq? x #f)) objs)))
-
-(export boolean=?)
-
 ;;; 6.4 Pairs and lists
 
 (define (member obj list . opts)
diff --git a/src/bool.c b/src/bool.c
index a985c625..74018c63 100644
--- a/src/bool.c
+++ b/src/bool.c
@@ -169,6 +169,25 @@ pic_bool_boolean_p(pic_state *pic)
   return (pic_true_p(v) || pic_false_p(v)) ? pic_true_value() : pic_false_value();
 }
 
+static pic_value
+pic_bool_boolean_eq_p(pic_state *pic)
+{
+  size_t argc, i;
+  pic_value *argv;
+
+  pic_get_args(pic, "*", &argc, &argv);
+
+  for (i = 0; i < argc; ++i) {
+    if (! (pic_true_p(argv[i]) || pic_false_p(argv[i]))) {
+      return pic_false_value();
+    }
+    if (! pic_eq_p(argv[i], argv[0])) {
+      return pic_false_value();
+    }
+  }
+  return pic_true_value();
+}
+
 void
 pic_init_bool(pic_state *pic)
 {
@@ -178,4 +197,5 @@ pic_init_bool(pic_state *pic)
 
   pic_defun(pic, "not", pic_bool_not);
   pic_defun(pic, "boolean?", pic_bool_boolean_p);
+  pic_defun(pic, "boolean=?", pic_bool_boolean_eq_p);
 }