diff --git a/CHANGES/674.bugfix b/CHANGES/674.bugfix
new file mode 100644
index 00000000..61d3a816
--- /dev/null
+++ b/CHANGES/674.bugfix
@@ -0,0 +1 @@
+Fixed incorrect type checking in the :class:`aiogram.utils.keyboard.KeyboardBuilder`
diff --git a/aiogram/utils/keyboard.py b/aiogram/utils/keyboard.py
index a8e31c17..56c5f1ff 100644
--- a/aiogram/utils/keyboard.py
+++ b/aiogram/utils/keyboard.py
@@ -232,7 +232,7 @@ class KeyboardBuilder(Generic[ButtonType]):
         return self.add(button)
 
     def as_markup(self, **kwargs: Any) -> Union[InlineKeyboardMarkup, ReplyKeyboardMarkup]:
-        if self._button_type is ReplyKeyboardMarkup:
+        if self._button_type is KeyboardButton:
             return ReplyKeyboardMarkup(keyboard=self.export(), **kwargs)
         return InlineKeyboardMarkup(inline_keyboard=self.export())