diff --git a/ChangeLog b/ChangeLog
index c1601492c5..bd6b1e982c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Jul 14 11:08:28 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* ext/json/ext/generator/generator.c (check_max_nesting): wrong
+	  format specifier.  a patch from pegacorn <subscriber.jp AT gmail.com>.
+	  [ruby-dev:31217]
+
 Sat Jul 14 02:27:43 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* numeric.c (int_pow): overflow detection using FIT_SQRT_LONG().
diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index 446235c695..cc639f9a34 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -9,7 +9,7 @@
 #define check_max_nesting(state, depth) do {                                   \
     long current_nesting = 1 + depth;                                          \
     if (state->max_nesting != 0 && current_nesting > state->max_nesting)       \
-        rb_raise(eNestingError, "nesting of %u is too deep", current_nesting); \
+        rb_raise(eNestingError, "nesting of %ld is too deep", current_nesting); \
 } while (0);
 
 static VALUE mJSON, mExt, mGenerator, cState, mGeneratorMethods, mObject,