diff --git a/lib/block-supports/duotone.php b/lib/block-supports/duotone.php
index f3b4743832f0ae..aa38c55f4bd5b1 100644
--- a/lib/block-supports/duotone.php
+++ b/lib/block-supports/duotone.php
@@ -351,7 +351,15 @@ function ( $selector ) use ( $duotone_id ) {
 		1
 	);
 
-	return $content . $duotone;
+	add_action(
+		// Ideally we should use wp_head, but SVG defs can't be put in there.
+		'wp_footer',
+		function () use ( $duotone ) {
+			echo $duotone;
+		}
+	);
+
+	return $content;
 }
 
 // Register the block support.