diff --git a/aula202-calculadora/buttons.py b/aula202-calculadora/buttons.py
index 98fe96b..a7b971c 100644
--- a/aula202-calculadora/buttons.py
+++ b/aula202-calculadora/buttons.py
@@ -1,7 +1,7 @@
 from display import Display
 from PySide6.QtCore import Slot
 from PySide6.QtWidgets import QGridLayout, QPushButton
-from utils import isEmpty, isNumOrDot
+from utils import isEmpty, isNumOrDot, isValidNumber
 from variables import MEDIUM_FONT_SIZE
 
 
@@ -15,7 +15,6 @@ class Button(QPushButton):
         font.setPixelSize(MEDIUM_FONT_SIZE)
         self.setFont(font)
         self.setMinimumSize(75, 75)
-        self.setCheckable(True)
 
 
 class ButtonsGrid(QGridLayout):
@@ -54,5 +53,10 @@ class ButtonsGrid(QGridLayout):
         return realSlot
 
     def _insertButtonTextToDisplay(self, button):
-        button_text = button.text()
-        self.display.insert(button_text)
+        buttonText = button.text()
+        newDisplayValue = self.display.text() + buttonText
+
+        if not isValidNumber(newDisplayValue):
+            return
+
+        self.display.insert(buttonText)
diff --git a/aula202-calculadora/utils.py b/aula202-calculadora/utils.py
index 67e662b..e28ca00 100644
--- a/aula202-calculadora/utils.py
+++ b/aula202-calculadora/utils.py
@@ -7,5 +7,15 @@ def isNumOrDot(string: str):
     return bool(NUM_OR_DOT_REGEX.search(string))
 
 
+def isValidNumber(string: str):
+    valid = False
+    try:
+        float(string)
+        valid = True
+    except ValueError:
+        valid = False
+    return valid
+
+
 def isEmpty(string: str):
     return len(string) == 0