diff --git a/src/PIL/ImageFont.py b/src/PIL/ImageFont.py
index c2956213519..1324f8b4e6f 100644
--- a/src/PIL/ImageFont.py
+++ b/src/PIL/ImageFont.py
@@ -790,6 +790,10 @@ def truetype(font=None, size=10, index=0, encoding="", layout_engine=None):
     :exception OSError: If the file could not be read.
     """
 
+    if size <= 0:
+        msg = "font size must be positive"
+        raise ValueError(msg)
+
     def freetype(font):
         return FreeTypeFont(font, size, index, encoding, layout_engine)