diff --git a/ChangeLog b/ChangeLog
index 3fa801b179..06b002cb30 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Mar  5 11:58:30 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/openssl/ossl.c (ossl_make_error): check NULL for unknown
+	  error reasons with old OpenSSL, and insert a colon iff formatted
+	  message is not empty.
+
 Wed Mar  5 00:42:00 2014  Kazuki Tsujimoto  <kazuki@callcc.net>
 
 	* ext/pathname/lib/pathname.rb (Pathname#find): add "ignore_error"
diff --git a/ext/openssl/ossl.c b/ext/openssl/ossl.c
index 614d2fa6f7..7f9105c117 100644
--- a/ext/openssl/ossl.c
+++ b/ext/openssl/ossl.c
@@ -312,10 +312,11 @@ ossl_make_error(VALUE exc, const char *fmt, va_list args)
 	else
 	    msg = ERR_reason_error_string(e);
 	if (NIL_P(str)) {
-	    str = rb_str_new_cstr(msg);
+	    if (msg) str = rb_str_new_cstr(msg);
 	}
 	else {
-	    rb_str_cat2(rb_str_cat2(str, ": "), msg);
+	    if (RSTRING_LEN(str)) rb_str_cat2(str, ": ");
+	    rb_str_cat2(str, msg ? msg : "(null)");
 	}
     }
     if (dOSSL == Qtrue){ /* show all errors on the stack */