diff --git a/ChangeLog b/ChangeLog
index 52daaa9ff6..3bc9be8586 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jul  9 21:20:22 2010  Tanaka Akira  <akr@fsij.org>
+
+	* strftime.c (rb_strftime_with_timespec): clear colons at unknown
+	  directive.
+
 Fri Jul  9 21:04:10 2010  Tanaka Akira  <akr@fsij.org>
 
 	* strftime.c: don't call tzset.  strftime.c doesn't depend on
diff --git a/strftime.c b/strftime.c
index b404b7812c..4f1481de7d 100644
--- a/strftime.c
+++ b/strftime.c
@@ -771,6 +771,7 @@ rb_strftime_with_timespec(char *s, size_t maxsize, const char *format, const str
 			precision = -1;
 			flags = 0;
 			padding = 0;
+                        colons = 0;
 			break;
 		}
 		if (i) {