diff --git a/libheif/image-items/mask_image.h b/libheif/image-items/mask_image.h
index c61befdb2c..c858bffa37 100644
--- a/libheif/image-items/mask_image.h
+++ b/libheif/image-items/mask_image.h
@@ -66,7 +66,7 @@ class Box_mskC : public FullBox
   Error parse(BitstreamRange& range, const heif_security_limits* limits) override;
 
 private:
-  uint8_t m_bits_per_pixel;
+  uint8_t m_bits_per_pixel = 0;
 };
 
 class MaskImageCodec