diff --git a/ChangeLog b/ChangeLog
index f277ed0719..cf507ee2f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Mar  6 15:16:55 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* sprintf.c (rb_str_format): casting double to long is undefined
+	  if the interger part of double is out of the range of long.
+
 Thu Mar  6 15:11:40 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* sprintf.c (rb_str_format): ignore 0 flag for NaN and Inf.
diff --git a/sprintf.c b/sprintf.c
index f5b3e8474a..795af92373 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -540,7 +540,8 @@ rb_str_format(int argc, const VALUE *argv, VALUE fmt)
 	      bin_retry:
 		switch (TYPE(val)) {
 		  case T_FLOAT:
-		    if (FIXABLE((long)RFLOAT_VALUE(val))) {
+		    if (RFLOAT_VALUE(val) <= LONG_MAX &&
+			RFLOAT_VALUE(val) >= LONG_MIN) {
 			val = LONG2FIX((long)RFLOAT_VALUE(val));
 			goto bin_retry;
 		    }