diff --git a/ChangeLog b/ChangeLog
index 5f187e9780..d7231176b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Apr  1 04:30:11 2010  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (long_mul): overflow condition changed.
+	  (wi_mul): ditto.
+
 Wed Mar 31 23:33:29 2010  Tanaka Akira  <akr@fsij.org>
 
 	* time.c (long_mul): extracted from mul and avoid integer overflow.
diff --git a/time.c b/time.c
index 05b7cd88f6..a3195e27a2 100644
--- a/time.c
+++ b/time.c
@@ -103,8 +103,8 @@ long_mul(long x, long y, long *z)
     else {
 	b = (unsigned long)y;
     }
-    c = a * b;
-    if (c / b == a) {
+    if (a <= ULONG_MAX / b) {
+        c = a * b;
 	if (s < 0) {
 	    if (c <= (unsigned long)LONG_MAX + 1) {
 		*z = -(long)c;
@@ -478,8 +478,8 @@ wi_mul(wideint_t x, wideint_t y, wideint_t *z)
     else {
 	b = (uwideint_t)y;
     }
-    c = a * b;
-    if (c / b == a) {
+    if (a <= UWIDEINT_MAX / b) {
+        c = a * b;
 	if (s < 0) {
 	    if (c <= (uwideint_t)WIDEINT_MAX + 1) {
 		*z = -(wideint_t)c;