diff --git a/src/network/mcpe/convert/LegacySkinAdapter.php b/src/network/mcpe/convert/LegacySkinAdapter.php
index 898036697..3a930095b 100644
--- a/src/network/mcpe/convert/LegacySkinAdapter.php
+++ b/src/network/mcpe/convert/LegacySkinAdapter.php
@@ -31,6 +31,7 @@ use function is_array;
 use function is_string;
 use function json_decode;
 use function json_encode;
+use function json_last_error_msg;
 use function random_bytes;
 use function str_repeat;
 
@@ -43,9 +44,13 @@ class LegacySkinAdapter implements SkinAdapter{
 		if($geometryName === ""){
 			$geometryName = "geometry.humanoid.custom";
 		}
+		$resourcePatch = json_encode(["geometry" => ["default" => $geometryName]]);
+		if($resourcePatch === false){
+			throw new \RuntimeException("json_encode() failed: " . json_last_error_msg());
+		}
 		return new SkinData(
 			$skin->getSkinId(),
-			json_encode(["geometry" => ["default" => $geometryName]]),
+			$resourcePatch,
 			SkinImage::fromLegacy($skin->getSkinData()), [],
 			$capeImage,
 			$skin->getGeometryData()