diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5a18857556..3d8d9364bd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2013-10-06  Yao Qi  <yao@codesourcery.com>
+
+	* varobj.h: Add comments to enum varobj_languages.
+
 2013-10-04  Doug Evans  <dje@google.com>
 
 	Add support for DWP file format version 2.
diff --git a/gdb/varobj.h b/gdb/varobj.h
index d4abb99762..b29e499d46 100644
--- a/gdb/varobj.h
+++ b/gdb/varobj.h
@@ -52,7 +52,8 @@ enum varobj_scope_status
 /* String representations of gdb's format codes (defined in varobj.c).  */
 extern char *varobj_format_string[];
 
-/* Languages supported by this variable objects system.  */
+/* Languages supported by this variable objects system.  This enum is used
+   to index arrays so we make its first enum explicitly zero.  */
 enum varobj_languages
   {
     vlang_c = 0, vlang_cplus, vlang_java, vlang_ada, vlang_end