diff --git a/ChangeLog b/ChangeLog
index 897d0228e5..d4c33aac74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jul 17 21:31:46 2008  Tanaka Akira  <akr@fsij.org>
+
+	* string.c (rb_str_format_m): make tmp volatile to avoid possible GC
+	  problem.
+
 Thu Jul 17 21:29:34 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/optparse.rb (OptionParser#environment): requires shellwords.
diff --git a/string.c b/string.c
index cb619f86b3..2f380e1ec7 100644
--- a/string.c
+++ b/string.c
@@ -455,7 +455,7 @@ static VALUE
 rb_str_format_m(str, arg)
     VALUE str, arg;
 {
-    VALUE tmp = rb_check_array_type(arg);
+    volatile VALUE tmp = rb_check_array_type(arg);
 
     if (!NIL_P(tmp)) {
 	return rb_str_format(RARRAY_LEN(tmp), RARRAY_PTR(tmp), str);
diff --git a/version.h b/version.h
index f6b4dc98ca..777859941d 100644
--- a/version.h
+++ b/version.h
@@ -2,7 +2,7 @@
 #define RUBY_RELEASE_DATE "2008-07-17"
 #define RUBY_VERSION_CODE 186
 #define RUBY_RELEASE_CODE 20080717
-#define RUBY_PATCHLEVEL 277
+#define RUBY_PATCHLEVEL 278
 
 #define RUBY_VERSION_MAJOR 1
 #define RUBY_VERSION_MINOR 8