diff --git a/inc/vk-blocks/languages/vk-blocks-js.pot b/inc/vk-blocks/languages/vk-blocks-js.pot
index 2f62d6f45..ddec14574 100644
--- a/inc/vk-blocks/languages/vk-blocks-js.pot
+++ b/inc/vk-blocks/languages/vk-blocks-js.pot
@@ -817,7 +817,7 @@ msgid "Pagination Type"
 msgstr ""
 
 #: src/blocks/_pro/slider/edit.js:285
-#: src/blocks/heading/edit.js:342
+#: src/blocks/heading/edit.js:344
 msgid "Hide"
 msgstr ""
 
@@ -1458,7 +1458,7 @@ msgstr ""
 msgid "Display"
 msgstr ""
 
-#: src/blocks/heading/edit.js:350
+#: src/blocks/heading/edit.js:352
 msgid "Text size (rem)"
 msgstr ""
 
diff --git a/inc/vk-blocks/languages/vk-blocks.pot b/inc/vk-blocks/languages/vk-blocks.pot
index b195310ba..4876c1522 100644
--- a/inc/vk-blocks/languages/vk-blocks.pot
+++ b/inc/vk-blocks/languages/vk-blocks.pot
@@ -9,7 +9,7 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
-"POT-Creation-Date: 2021-07-19T06:28:49+00:00\n"
+"POT-Creation-Date: 2021-07-20T00:15:44+00:00\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "X-Generator: WP-CLI 2.4.0\n"
 "X-Domain: vk-blocks\n"
@@ -824,7 +824,7 @@ msgid "Pagination Type"
 msgstr ""
 
 #: src/blocks/_pro/slider/edit.js:285
-#: src/blocks/heading/edit.js:342
+#: src/blocks/heading/edit.js:344
 msgid "Hide"
 msgstr ""
 
@@ -1461,7 +1461,7 @@ msgstr ""
 msgid "Display"
 msgstr ""
 
-#: src/blocks/heading/edit.js:350
+#: src/blocks/heading/edit.js:352
 msgid "Text size (rem)"
 msgstr ""
 
diff --git a/src/blocks/bundle.js b/src/blocks/bundle.js
index 04b849c22..d50447309 100644
--- a/src/blocks/bundle.js
+++ b/src/blocks/bundle.js
@@ -80,8 +80,18 @@ const registerBlock = (block) => {
 
 	let { metadata, settings, name } = block;
 
+	/*
+	そもそも Require at Least が 5.7 なので 5.5 以下の後方互換は不要ではあるが、現状影響が少ないので残しておく
+	window.wpVersion は外観 > カスタマイズ > ウィジェットでは undefined を返すので比較不可能
+	ともかく最初から undefined が条件に当てはまらないように変更
+	*/
+
 	//WP5.5未満の場合
-	if (compareVersions(window.wpVersion, '5.5') < 0) {
+	if (
+		window.wpVersion !== undefined &&
+		window.wpVersion !== null &&
+		compareVersions(window.wpVersion, '5.5') < 0
+	) {
 		//nameを削除
 		delete metadata.name;
 		//カテゴリ等を追加