diff --git a/ChangeLog b/ChangeLog
index 7f0d3c6814..2c027ef85d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jul 15 14:13:02 2013  Masaki Matsushita  <glass.saga@gmail.com>
+
+	* struct.c (rb_struct_each_pair): use rb_yield_values(2, key, value)
+	  instead of rb_yield(rb_assoc_new(key, value)) if rb_block_arity()
+	  is greater than 1.
+
 Mon Jul 15 13:46:26 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c: Add static assertions.
diff --git a/struct.c b/struct.c
index 5dc5e73ae8..90af2d0568 100644
--- a/struct.c
+++ b/struct.c
@@ -524,10 +524,19 @@ rb_struct_each_pair(VALUE s)
 
     RETURN_SIZED_ENUMERATOR(s, 0, 0, struct_enum_size);
     members = rb_struct_members(s);
-    for (i=0; i<RSTRUCT_LEN(s); i++) {
-	VALUE key = rb_ary_entry(members, i);
-	VALUE value = RSTRUCT_GET(s, i);
-	rb_yield(rb_assoc_new(key, value));
+    if (rb_block_arity() > 1) {
+	for (i=0; i<RSTRUCT_LEN(s); i++) {
+	    VALUE key = rb_ary_entry(members, i);
+	    VALUE value = RSTRUCT_GET(s, i);
+	    rb_yield_values(2, key, value);
+	}
+    }
+    else {
+	for (i=0; i<RSTRUCT_LEN(s); i++) {
+	    VALUE key = rb_ary_entry(members, i);
+	    VALUE value = RSTRUCT_GET(s, i);
+	    rb_yield(rb_assoc_new(key, value));
+	}
     }
     return s;
 }