diff --git a/whiptail/__init__.py b/whiptail/__init__.py
index 5aaaf57..1128e61 100644
--- a/whiptail/__init__.py
+++ b/whiptail/__init__.py
@@ -306,7 +306,7 @@ def calc_height(self, msg: str) -> List[str]:
 		else:
 			height = self.height
 
-		return [str(height - height_offset)]
+		return [str(max(0, height - height_offset))]
 
 	def menu(
 			self,