diff --git a/.eslintrc.js b/.eslintrc.js
index 50bb0e29d3..b3f6f5a712 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -25,6 +25,17 @@ module.exports = {
         endOfLine: "auto",
       },
     ],
+    "vue/no-restricted-syntax": [
+      "error",
+      {
+        selector: "LogicalExpression[operator=??]",
+        message: `template内で"??"を使うとgithubのsyntax highlightが崩れるので\n三項演算子等を使って書き換えてください`,
+      },
+      {
+        selector: "MemberExpression[optional=true]",
+        message: `template内で"?."を使うとgithubのsyntax highlightが崩れるので\n三項演算子等を使って書き換えてください`,
+      },
+    ],
     "@typescript-eslint/no-unused-vars": [
       "warn",
       {
diff --git a/src/components/AudioInfo.vue b/src/components/AudioInfo.vue
index e35a7cbea8..07346a7fa7 100644
--- a/src/components/AudioInfo.vue
+++ b/src/components/AudioInfo.vue
@@ -170,7 +170,12 @@
         :class="{
           disabled: speedScaleSlider.qSliderProps.disable.value,
         }"
-        >話速 {{ speedScaleSlider.state.currentValue.value?.toFixed(2) }}</span
+        >話速
+        {{
+          speedScaleSlider.state.currentValue.value
+            ? speedScaleSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
@@ -196,7 +201,12 @@
         :class="{
           disabled: pitchScaleSlider.qSliderProps.disable.value,
         }"
-        >音高 {{ pitchScaleSlider.state.currentValue.value?.toFixed(2) }}</span
+        >音高
+        {{
+          pitchScaleSlider.state.currentValue.value
+            ? pitchScaleSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
@@ -223,7 +233,11 @@
           disabled: intonationScaleSlider.qSliderProps.disable.value,
         }"
         >抑揚
-        {{ intonationScaleSlider.state.currentValue.value?.toFixed(2) }}</span
+        {{
+          intonationScaleSlider.state.currentValue.value
+            ? intonationScaleSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
@@ -249,7 +263,12 @@
         :class="{
           disabled: volumeScaleSlider.qSliderProps.disable.value,
         }"
-        >音量 {{ volumeScaleSlider.state.currentValue.value?.toFixed(2) }}</span
+        >音量
+        {{
+          volumeScaleSlider.state.currentValue.value
+            ? volumeScaleSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
@@ -276,7 +295,11 @@
           disabled: prePhonemeLengthSlider.qSliderProps.disable.value,
         }"
         >開始無音
-        {{ prePhonemeLengthSlider.state.currentValue.value?.toFixed(2) }}</span
+        {{
+          prePhonemeLengthSlider.state.currentValue.value
+            ? prePhonemeLengthSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
@@ -303,7 +326,11 @@
           disabled: postPhonemeLengthSlider.qSliderProps.disable.value,
         }"
         >終了無音
-        {{ postPhonemeLengthSlider.state.currentValue.value?.toFixed(2) }}</span
+        {{
+          postPhonemeLengthSlider.state.currentValue.value
+            ? postPhonemeLengthSlider.state.currentValue.value.toFixed(2)
+            : undefined
+        }}</span
       >
       <q-slider
         dense
diff --git a/src/components/AudioParameter.vue b/src/components/AudioParameter.vue
index f98692abb0..c633ec9314 100644
--- a/src/components/AudioParameter.vue
+++ b/src/components/AudioParameter.vue
@@ -11,7 +11,11 @@
         !disable && (valueLabel.visible || previewSlider.state.isPanning.value)
       "
     >
-      {{ previewSlider.state.currentValue.value?.toFixed(precisionComputed) }}
+      {{
+        previewSlider.state.currentValue.value
+          ? previewSlider.state.currentValue.value.toFixed(precisionComputed)
+          : undefined
+      }}
     </q-badge>
     <q-slider
       vertical
diff --git a/src/components/CharacterOrderDialog.vue b/src/components/CharacterOrderDialog.vue
index 7ffc1a705e..78dafa71a6 100644
--- a/src/components/CharacterOrderDialog.vue
+++ b/src/components/CharacterOrderDialog.vue
@@ -72,7 +72,9 @@
                   <img
                     :src="
                       characterInfosMap[speakerUuid].metas.styles[
-                        selectedStyleIndexes[speakerUuid] ?? 0
+                        selectedStyleIndexes[speakerUuid]
+                          ? selectedStyleIndexes[speakerUuid]
+                          : 0
                       ].iconPath
                     "
                     class="style-icon"
diff --git a/src/components/HotkeySettingDialog.vue b/src/components/HotkeySettingDialog.vue
index a0a2e1e0a1..eede0bc615 100644
--- a/src/components/HotkeySettingDialog.vue
+++ b/src/components/HotkeySettingDialog.vue
@@ -175,7 +175,7 @@
           text-color="display-on-primary"
           class="q-mt-sm"
           @click="
-            changeHotkeySettings(lastAction, lastRecord)?.then(() =>
+            changeHotkeySettings(lastAction, lastRecord).then(() =>
               closeHotkeyDialog()
             )
           "
@@ -189,7 +189,7 @@
           color="primary"
           text-color="display-on-primary"
           class="q-mt-sm"
-          @click="solveDuplicated()?.then(() => closeHotkeyDialog())"
+          @click="solveDuplicated().then(() => closeHotkeyDialog())"
           :disabled="confirmBtnEnabled"
         />
       </q-card-actions>