diff --git a/sakura_core/charset/codechecker.h b/sakura_core/charset/codechecker.h
index 738a24e7cf..5a2e483c5a 100644
--- a/sakura_core/charset/codechecker.h
+++ b/sakura_core/charset/codechecker.h
@@ -392,8 +392,7 @@ char32_t ConvertToUtf32(std::wstring_view text) {
  * 文字列がIVSの異体字セレクタで始まっているか判定する
  */
 inline bool IsVariationSelector(std::wstring_view text) {
-	const auto cp = ConvertToUtf32(text);
-	return 0xe0100 <= cp && cp <= 0xe01ef;
+	return (2 <= text.size()) && (text[0] == 0xDB40) && (0xDD00 <= text[1]) && (text[1] <= 0xDDEF);
 }
 
 //! 上位バイトと下位バイトを交換 (主に UTF-16 LE/BE 向け)
diff --git a/sakura_core/mem/CNativeW.cpp b/sakura_core/mem/CNativeW.cpp
index dbd8e8a98d..1365913ff2 100644
--- a/sakura_core/mem/CNativeW.cpp
+++ b/sakura_core/mem/CNativeW.cpp
@@ -397,7 +397,7 @@ CLogicInt CNativeW::GetSizeOfChar( const wchar_t* pData, int nDataLen, int nIdx
 	}
 
 	// IVSの異体字セレクタチェック
-	if (IsVariationSelector(pData + nIdx + 1)) {
+	if (IsVariationSelector(std::wstring_view(pData + nIdx + 1, nDataLen - (nIdx + 1)))) {
 		// 正字 + 異体字セレクタで3個分
 		return CLogicInt(3);
 	}
diff --git a/sakura_core/parse/CWordParse.cpp b/sakura_core/parse/CWordParse.cpp
index b1f46c98d7..a09f7cf3d6 100644
--- a/sakura_core/parse/CWordParse.cpp
+++ b/sakura_core/parse/CWordParse.cpp
@@ -187,7 +187,7 @@ ECharKind CWordParse::WhatKindOfChar(
 	}
 	// IVS（正字 + 異体字セレクタ）
 	else if (nCharChars == 3 &&
-		IsVariationSelector(pData + nIdx + 1))
+		IsVariationSelector(std::wstring_view(pData + nIdx + 1, pDataLen - (nIdx + 1))))
 	{
 		ret = CK_ZEN_ETC;				// 全角のその他(漢字など)
 	}
diff --git a/sakura_core/view/CTextMetrics.cpp b/sakura_core/view/CTextMetrics.cpp
index 182c849031..9d225b3d15 100644
--- a/sakura_core/view/CTextMetrics.cpp
+++ b/sakura_core/view/CTextMetrics.cpp
@@ -109,7 +109,7 @@ const int* CTextMetrics::GenerateDxArray(
 		vResultArray.push_back(cache.CalcPxWidthByFont(pText[i]) + spacing);
 		nIndent += vResultArray.back();
 
-		if (IsVariationSelector(pText + i + 1)) {
+		if (IsVariationSelector(std::wstring_view(pText + i + 1, nLength - (i + 1)))) {
 			vResultArray.push_back(0);
 			vResultArray.push_back(0);
 			i += 2;
diff --git a/tests/unittests/test-codechecker.cpp b/tests/unittests/test-codechecker.cpp
index f7d84b1b01..1b5c2f9aa0 100644
--- a/tests/unittests/test-codechecker.cpp
+++ b/tests/unittests/test-codechecker.cpp
@@ -45,3 +45,24 @@ TEST(ConvertToUtf32, BinaryOnSurrogate)
 	const auto& s = L"\xdcff";
 	EXPECT_EQ(0, ConvertToUtf32(s));
 }
+
+TEST(IsVariationSelector, VariationSelectorCheck)
+{
+	// 異体字セレクタ開始
+	const auto& vs1 = L"\U000E0100";
+	EXPECT_TRUE(IsVariationSelector(vs1));
+
+	// 異体字セレクタ終了
+	const auto& vs2 = L"\U000E01EF";
+	EXPECT_TRUE(IsVariationSelector(vs2));
+
+	// 非該当文字列
+	const auto& notvs1 = L"";
+	EXPECT_FALSE(IsVariationSelector(notvs1));
+	const auto& notvs2 = L"\xDB40";
+	EXPECT_FALSE(IsVariationSelector(notvs2));
+	const auto& notvs3 = L"\U000E00FF";
+	EXPECT_FALSE(IsVariationSelector(notvs3));
+	const auto& notvs4 = L"\U000E01F0";
+	EXPECT_FALSE(IsVariationSelector(notvs4));
+}
diff --git a/tests/unittests/test-ctextmetrics.cpp b/tests/unittests/test-ctextmetrics.cpp
index 4dfeee8970..1e0f2d0af8 100644
--- a/tests/unittests/test-ctextmetrics.cpp
+++ b/tests/unittests/test-ctextmetrics.cpp
@@ -225,7 +225,7 @@ TEST(CTextMetrics, GenerateDxArray8)
 	// IVSのVariantSelectorが続く文字列は先頭1文字 + 幅0×2で生成する
 	std::vector<int> v;
 	FakeCache1 cache;
-	CTextMetrics::GenerateDxArray(&v, L"葛󠄀", 2, 0, 0, 0, 10, cache);
+	CTextMetrics::GenerateDxArray(&v, L"葛󠄀", 3, 0, 0, 0, 10, cache);
 	EXPECT_TRUE(v[0]);
 	EXPECT_FALSE(v[1]);
 	EXPECT_FALSE(v[2]);