diff --git a/ChangeLog b/ChangeLog
index f31c2f01ae..1bf731c159 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sun Nov 17 01:43:33 2013  Tanaka Akira  <akr@fsij.org>
+
+	* thread_pthread.c (rb_thread_create_timer_thread): Show error
+	  message instead of error number.
+
+	* cont.c (fiber_machine_stack_alloc): Ditto.
+
 Sat Nov 16 18:28:08 2013  Kouhei Sutou  <kou@cozmixng.org>
 
 	* lib/rexml/parsers/ultralightparser.rb
diff --git a/cont.c b/cont.c
index 22eabb6451..fa9e91ee64 100644
--- a/cont.c
+++ b/cont.c
@@ -625,7 +625,7 @@ fiber_machine_stack_alloc(size_t size)
 	errno = 0;
 	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, FIBER_STACK_FLAGS, -1, 0);
 	if (ptr == MAP_FAILED) {
-	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber errno: %d", errno);
+	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber: %s", strerror(errno));
 	}
 
 	/* guard page setup */
diff --git a/thread_pthread.c b/thread_pthread.c
index 3911f8fcff..10ef8daab3 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1470,7 +1470,7 @@ rb_thread_create_timer_thread(void)
 
 	err = pthread_attr_init(&attr);
 	if (err != 0) {
-	    fprintf(stderr, "[FATAL] Failed to initialize pthread attr(errno: %d)\n", err);
+	    fprintf(stderr, "[FATAL] Failed to initialize pthread attr: %s\n", strerror(err));
 	    exit(EXIT_FAILURE);
         }
 # ifdef PTHREAD_STACK_MIN
@@ -1503,7 +1503,7 @@ rb_thread_create_timer_thread(void)
 	err = pthread_create(&timer_thread_id, NULL, thread_timer, &GET_VM()->gvl);
 #endif
 	if (err != 0) {
-	    fprintf(stderr, "[FATAL] Failed to create timer thread (errno: %d)\n", err);
+	    fprintf(stderr, "[FATAL] Failed to create timer thread: %s\n", strerror(err));
 	    exit(EXIT_FAILURE);
 	}
 #ifdef HAVE_PTHREAD_ATTR_INIT