diff --git a/packages/block-library/src/post-featured-image/style.scss b/packages/block-library/src/post-featured-image/style.scss
index a7164e9fe0183e..07ccac4adc6fbe 100644
--- a/packages/block-library/src/post-featured-image/style.scss
+++ b/packages/block-library/src/post-featured-image/style.scss
@@ -8,4 +8,9 @@
 		max-width: 100%;
 		height: auto;
 	}
+
+	&.alignwide img,
+	&.alignfull img {
+		width: 100%;
+	}
 }