diff --git a/ChangeLog b/ChangeLog
index 2f59163ee8..5c5d08dbcf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Aug 27 19:04:06 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* internal.h (rb_strftime_timespec): moved from time.c and define only
+	  if ruby/encoding.h is included.
+
+	* internal.h (rb_strftime): ditto.
+
 Sat Aug 27 18:53:51 2011  Kazuki Tsujimoto  <kazuki@callcc.net>
 
 	* proc.c (proc_new): force to rewrite errinfo when calling Proc.new in ensure.
diff --git a/internal.h b/internal.h
index 3bd4d6a639..576ec32699 100644
--- a/internal.h
+++ b/internal.h
@@ -157,6 +157,14 @@ VALUE rb_reg_check_preprocess(VALUE);
 /* signal.c */
 int rb_get_next_signal(void);
 
+/* strftime.c */
+#ifdef RUBY_ENCODING_H
+size_t rb_strftime_timespec(char *s, size_t maxsize, const char *format, rb_encoding *enc,
+	const struct vtm *vtm, struct timespec *ts, int gmt);
+size_t rb_strftime(char *s, size_t maxsize, const char *format, rb_encoding *enc,
+            const struct vtm *vtm, VALUE timev, int gmt);
+#endif
+
 /* string.c */
 int rb_str_buf_cat_escaped_char(VALUE result, unsigned int c, int unicode_p);
 
diff --git a/time.c b/time.c
index c47b3569a0..f74b3c7b29 100644
--- a/time.c
+++ b/time.c
@@ -16,9 +16,6 @@
 #include "ruby/encoding.h"
 #include "internal.h"
 
-/* strftime.c */
-size_t rb_strftime_timespec(char *s, size_t maxsize, const char *format, rb_encoding *enc, const struct vtm *vtm, struct timespec *ts, int gmt);
-
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -4286,10 +4283,6 @@ time_to_a(VALUE time)
 		    time_zone(time));
 }
 
-size_t
-rb_strftime(char *s, size_t maxsize, const char *format, rb_encoding *enc,
-            const struct vtm *vtm, VALUE timev, int gmt);
-
 #define SMALLBUF 100
 static size_t
 rb_strftime_alloc(char **buf, const char *format, rb_encoding *enc,