diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 170443f..ae01ba4 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -6,12 +6,12 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [12, 14]
+        node-version: [ 20, 22 ]
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: setup Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
       - name: Install
diff --git a/package.json b/package.json
index ae6d6b5..c49a95e 100644
--- a/package.json
+++ b/package.json
@@ -57,5 +57,6 @@
     "*.{js,jsx,ts,tsx,css}": [
       "prettier --write"
     ]
-  }
+  },
+  "packageManager": "yarn@1.22.22+sha256.c17d3797fb9a9115bf375e31bfd30058cac6bc9c3b8807a3d8cb2094794b51ca"
 }
diff --git a/src/analyze.js b/src/analyze.js
index 747656c..712a7b7 100644
--- a/src/analyze.js
+++ b/src/analyze.js
@@ -50,11 +50,16 @@ export function isDearu({ type }) {
 }
 
 /**
- * typeが敬体(ですます調)か常体(である調)かを判定する
+ * typeが敬体(ですます調)なら true を返す
  * @param {string} type
  * @returns {boolean}
  */
 const isDesumasuType = (type) => type === Types.desu || type === Types.masu;
+/**
+ * typeが常体(である調)なら true を返す
+ * @param type
+ * @returns {boolean}
+ */
 const isDearuType = (type) => type === Types.dearu;
 
 /**
@@ -122,8 +127,7 @@ const mapToAnalyzedResult = (tokens) => {
         return {
             type: token["conjugated_type"],
             value: value,
-            surface: token["surface_form"],
-            // index start with 0
+            surface: token["surface_form"], // index start with 0
             index: token["word_position"] - 1,
             /**
              * @type {AnalyzedToken}
@@ -160,6 +164,12 @@ export function analyze(text, options = defaultOptions) {
                     }
                 }
             } else if (isDesumasuType(conjugatedType)) {
+                // "やす" は "特殊・マス" として認識されるが、誤判定を避けるために除外する
+                // https://github.com/textlint-ja/textlint-rule-no-mix-dearu-desumasu/issues/52
+                if (token["basic_form"] === "やす") {
+                    return false;
+                }
+
                 // TODO: can omit?
                 if (token["conjugated_form"] === "基本形") {
                     // 文末の"です"のみを許容する場合は、文末であるかどうかを調べる
diff --git a/test/analyze-test.js b/test/analyze-test.js
index 0b81901..a835c7d 100644
--- a/test/analyze-test.js
+++ b/test/analyze-test.js
@@ -139,6 +139,12 @@ describe("analyze-test", function () {
                     });
                 });
             });
+            it("'やす'はですます調としては認識しない", function () {
+                let text = "構成物の崩れやすさ、脆さに注意が必要である。";
+                return analyzeDesumasu(text).then((results) => {
+                    assert(results.length === 0);
+                });
+            });
         });
     });
     describe("analyzeDearu", function () {