diff --git a/bbp_ng/OP_EXPORT_virtools.py b/bbp_ng/OP_EXPORT_virtools.py
index 645374c..4979b0a 100644
--- a/bbp_ng/OP_EXPORT_virtools.py
+++ b/bbp_ng/OP_EXPORT_virtools.py
@@ -18,6 +18,12 @@ class BBP_OT_export_virtools(bpy.types.Operator, UTIL_file_browser.ExportVirtool
         return (
             PROP_preferences.get_raw_preferences().has_valid_blc_tex_folder()
             and bmap.is_bmap_available())
+
+    def invoke(self, context, event):
+        # preset virtools encoding if possible
+        self.preset_vt_encodings_if_possible(context)
+        # call parent invoke function (same reason written in IMPORT module)
+        return super().invoke(context, event)
     
     def execute(self, context):
         # check selecting first
diff --git a/bbp_ng/OP_IMPORT_virtools.py b/bbp_ng/OP_IMPORT_virtools.py
index 2919a70..611cef8 100644
--- a/bbp_ng/OP_IMPORT_virtools.py
+++ b/bbp_ng/OP_IMPORT_virtools.py
@@ -18,6 +18,12 @@ class BBP_OT_import_virtools(bpy.types.Operator, UTIL_file_browser.ImportVirtool
         return (
             PROP_preferences.get_raw_preferences().has_valid_blc_tex_folder()
             and bmap.is_bmap_available())
+
+    def invoke(self, context, event):
+        # preset virtools encoding if possible
+        self.preset_vt_encodings_if_possible(context)
+        # call parent invoke function (do no call self "execute", because we need show a modal window)
+        return super().invoke(context, event)
     
     def execute(self, context):
         # check whether encoding list is empty to avoid real stupid user.
diff --git a/bbp_ng/PROP_ptrprop_resolver.py b/bbp_ng/PROP_ptrprop_resolver.py
index 9c4b151..54295cb 100644
--- a/bbp_ng/PROP_ptrprop_resolver.py
+++ b/bbp_ng/PROP_ptrprop_resolver.py
@@ -195,6 +195,16 @@ class PropsVisitor():
     def get_ioport_encodings(self) -> tuple[str, ...]:
         encodings = get_ioport_encodings(self.__mAssocScene)
         return tuple(i.encoding for i in encodings)
+    def preset_ioport_encodings(self) -> None:
+        """
+        Set IOPort used encodings list as preset encoding list.
+        Please note that all old values will be overwritten.
+        """
+        encodings = get_ioport_encodings(self.__mAssocScene)
+        encodings.clear()
+        for default_enc in UTIL_virtools_types.g_PyBMapDefaultEncodings:
+            item = encodings.add()
+            item.encoding = default_enc
     def draw_ioport_encodings(self, layout: bpy.types.UILayout) -> None:
         target = get_ptrprop_resolver(self.__mAssocScene)
         row = layout.row()
@@ -218,24 +228,11 @@ class PropsVisitor():
         col.separator()
         col.operator(BBP_OT_clear_ioport_encodings.bl_idname, icon='TRASH', text='')
 
-@bpy.app.handlers.persistent
-def _ioport_encodings_initializer(file_path: str):
-    # if we can fetch property, and it is empty after loading file
-    # we fill it with default value
-    encodings = get_ioport_encodings(bpy.context.scene)
-    if len(encodings) == 0:
-        for default_enc in UTIL_virtools_types.g_PyBMapDefaultEncodings:
-            item = encodings.add()
-            item.encoding = default_enc
-
 def register() -> None:
     bpy.utils.register_class(BBP_PG_bmap_encoding)
     bpy.utils.register_class(BBP_UL_bmap_encoding)
     bpy.utils.register_class(BBP_PG_ptrprop_resolver)
 
-    # register ioport encodings default value
-    bpy.app.handlers.load_post.append(_ioport_encodings_initializer)
-
     bpy.utils.register_class(BBP_OT_add_ioport_encodings)
     bpy.utils.register_class(BBP_OT_rm_ioport_encodings)
     bpy.utils.register_class(BBP_OT_up_ioport_encodings)
@@ -253,9 +250,6 @@ def unregister() -> None:
     bpy.utils.unregister_class(BBP_OT_rm_ioport_encodings)
     bpy.utils.unregister_class(BBP_OT_add_ioport_encodings)
 
-    # unregister ioport encodings default value
-    bpy.app.handlers.load_post.remove(_ioport_encodings_initializer)
-
     bpy.utils.unregister_class(BBP_PG_ptrprop_resolver)
     bpy.utils.unregister_class(BBP_UL_bmap_encoding)
     bpy.utils.unregister_class(BBP_PG_bmap_encoding)
diff --git a/bbp_ng/UTIL_ioport_shared.py b/bbp_ng/UTIL_ioport_shared.py
index 45a991f..ac2fe2f 100644
--- a/bbp_ng/UTIL_ioport_shared.py
+++ b/bbp_ng/UTIL_ioport_shared.py
@@ -340,6 +340,14 @@ class VirtoolsParams():
         translation_context = 'BBP/UTIL_ioport_shared.VirtoolsParams/property'
     ) # type: ignore
 
+    def preset_vt_encodings_if_possible(self, context: bpy.types.Context):
+        """
+        Set preset value for Virtools Encoding list if there is no value inside it.
+        """
+        ptrprops = PROP_ptrprop_resolver.PropsVisitor(context.scene)
+        if len(ptrprops.get_ioport_encodings()) == 0:
+            ptrprops.preset_ioport_encodings()
+
     def draw_virtools_params(self, context: bpy.types.Context, layout: bpy.types.UILayout, is_importer: bool) -> None:
         header: bpy.types.UILayout
         body: bpy.types.UILayout
@@ -364,7 +372,6 @@ class VirtoolsParams():
             if self.use_compress:
                 body.prop(self, 'compress_level')
 
-
     def general_get_vt_encodings(self, context: bpy.types.Context) -> tuple[str, ...]:
         # get from ptrprop resolver then filter empty item
         ptrprops = PROP_ptrprop_resolver.PropsVisitor(context.scene)