diff --git a/ChangeLog.adoc b/ChangeLog.adoc
index 8db9cc176..fcc45803d 100644
--- a/ChangeLog.adoc
+++ b/ChangeLog.adoc
@@ -24,6 +24,7 @@ New features::
 
 Improvements::
 
+  * core: add a warning in header of configuration files to not edit by hand (issue #851)
   * irc: change default value of option irc.network.lag_reconnect to 300 (issue #818)
   * trigger: do not hide email in command "/msg nickserv register password email" (issue #849)
 
diff --git a/src/core/wee-config-file.c b/src/core/wee-config-file.c
index 7a6f3591f..156e3d4bb 100644
--- a/src/core/wee-config-file.c
+++ b/src/core/wee-config-file.c
@@ -2459,13 +2459,23 @@ config_file_write_internal (struct t_config_file *config_file,
     }
 
     /* write header with name of config file and WeeChat version */
-    if (!string_fprintf (config_file->file, "#\n"))
-        goto error;
-    if (!string_fprintf (config_file->file,
-                         "# %s -- %s\n#\n",
-                         version_get_name (),
-                         config_file->filename))
+    if (!string_fprintf (
+            config_file->file,
+            "#\n"
+            "# %s -- %s\n"
+            "#\n"
+            "# WARNING: It is NOT recommended to edit this file by hand,\n"
+            "# especially if WeeChat is running.\n"
+            "#\n"
+            "# Use /set or similar command to change settings in WeeChat.\n"
+            "#\n"
+            "# For more info, see: https://weechat.org/doc/quickstart\n"
+            "#\n",
+            version_get_name (),
+            config_file->filename))
+    {
         goto error;
+    }
 
     /* write all sections */
     for (ptr_section = config_file->sections; ptr_section;