diff --git a/src/pair.c b/src/pair.c
index d8bb8d70..5b62ceaf 100644
--- a/src/pair.c
+++ b/src/pair.c
@@ -25,7 +25,7 @@ pic_car(pic_state *pic, pic_value obj)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required, but got ~s", obj);
   }
   pair = pic_pair_ptr(obj);
 
@@ -38,7 +38,7 @@ pic_cdr(pic_state *pic, pic_value obj)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required, but got ~s", obj);
   }
   pair = pic_pair_ptr(obj);