diff --git a/apps/emqx/src/emqx_schema.erl b/apps/emqx/src/emqx_schema.erl
index 4a23bfeda..b4cb63fc4 100644
--- a/apps/emqx/src/emqx_schema.erl
+++ b/apps/emqx/src/emqx_schema.erl
@@ -57,6 +57,7 @@
     validate_heap_size/1,
     parse_user_lookup_fun/1,
     validate_alarm_actions/1,
+    non_empty_string/1,
     validations/0
 ]).
 
@@ -1898,6 +1899,7 @@ client_ssl_opts_schema(Defaults1) ->
                     hoconsc:union([disable, string()]),
                     #{
                         required => false,
+                        validator => fun emqx_schema:non_empty_string/1,
                         desc => ?DESC(client_ssl_opts_schema_server_name_indication)
                     }
                 )}
@@ -2177,3 +2179,8 @@ authentication(Type) ->
 -spec qos() -> typerefl:type().
 qos() ->
     typerefl:alias("qos", typerefl:union([0, 1, 2])).
+
+non_empty_string(<<>>) -> {error, empty_string_not_allowed};
+non_empty_string("") -> {error, empty_string_not_allowed};
+non_empty_string(S) when is_binary(S); is_list(S) -> ok;
+non_empty_string(_) -> {error, invalid_string}.
diff --git a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
index 2a0fcc3fa..d913e1ecf 100644
--- a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
+++ b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
@@ -31,8 +31,6 @@
         , egress_desc/0
         ]).
 
--export([non_empty_string/1]).
-
 -import(emqx_schema, [mk_duration/2]).
 
 namespace() -> "connector-mqtt".
@@ -98,7 +96,7 @@ fields("ingress") ->
     [ {remote_topic,
         sc(binary(),
            #{ required => true
-            , validator => fun ?MODULE:non_empty_string/1
+            , validator => fun emqx_schema:non_empty_string/1
             , desc => ?DESC("ingress_remote_topic")
             })}
     , {remote_qos,
@@ -108,7 +106,7 @@ fields("ingress") ->
             })}
     , {local_topic,
         sc(binary(),
-           #{ validator => fun ?MODULE:non_empty_string/1
+           #{ validator => fun emqx_schema:non_empty_string/1
             , desc => ?DESC("ingress_local_topic")
             })}
     , {local_qos,
@@ -140,12 +138,12 @@ fields("egress") ->
     [ {local_topic,
         sc(binary(),
            #{ desc => ?DESC("egress_local_topic")
-            , validator => fun ?MODULE:non_empty_string/1
+            , validator => fun emqx_schema:non_empty_string/1
             })}
     , {remote_topic,
         sc(binary(),
            #{ required => true
-            , validator => fun ?MODULE:non_empty_string/1
+            , validator => fun emqx_schema:non_empty_string/1
             , desc => ?DESC("egress_remote_topic")
             })}
     , {remote_qos,
@@ -228,10 +226,5 @@ local_topic will be forwarded.
 qos() ->
     hoconsc:union([emqx_schema:qos(), binary()]).
 
-non_empty_string(<<>>) -> {error, empty_string_not_allowed};
-non_empty_string("") -> {error, empty_string_not_allowed};
-non_empty_string(S) when is_binary(S); is_list(S) -> ok;
-non_empty_string(_) -> {error, invalid_string}.
-
 sc(Type, Meta) -> hoconsc:mk(Type, Meta).
 ref(Field) -> hoconsc:ref(?MODULE, Field).