diff --git a/mvc/controllers.py b/mvc/controllers.py
index 0c1d1cb..4e327f6 100644
--- a/mvc/controllers.py
+++ b/mvc/controllers.py
@@ -18,7 +18,11 @@ class EditController:
             case self.adapter.KEY_BACKSPACE_1: self.model.Backspace()
             case self.adapter.KEY_BACKSPACE_2: self.model.Backspace()
             case self.adapter.KEY_CTRL_S: self.model.SaveFile()
-            case _: self.model.InsertSymbol(symbolCode)
+            case _:
+                if symbolCode > 127 or symbolCode < 0:
+                    print("Only 1-byte symbols!")
+                    return False
+                self.model.InsertSymbol(symbolCode)
 
         self.model.Scroll(self.adapter.lines, self.adapter.cols)
         return True
\ No newline at end of file