diff --git a/app/src/main/java/io/legado/app/data/entities/BaseBook.kt b/app/src/main/java/io/legado/app/data/entities/BaseBook.kt
index 6a7d561ee..144f59ec4 100644
--- a/app/src/main/java/io/legado/app/data/entities/BaseBook.kt
+++ b/app/src/main/java/io/legado/app/data/entities/BaseBook.kt
@@ -3,7 +3,7 @@ package io.legado.app.data.entities
 import io.legado.app.utils.splitNotBlank
 
 interface BaseBook {
-    var variableMap: HashMap<String, String>?
+    var variableMap: HashMap<String, String>
     var kind: String?
     var wordCount: String?
 
diff --git a/app/src/main/java/io/legado/app/data/entities/Book.kt b/app/src/main/java/io/legado/app/data/entities/Book.kt
index 118acf35b..0ab5a9879 100644
--- a/app/src/main/java/io/legado/app/data/entities/Book.kt
+++ b/app/src/main/java/io/legado/app/data/entities/Book.kt
@@ -1,7 +1,6 @@
 package io.legado.app.data.entities
 
 import android.os.Parcelable
-import android.text.TextUtils.isEmpty
 import androidx.room.Entity
 import androidx.room.Ignore
 import androidx.room.Index
@@ -50,11 +49,7 @@ data class Book(
 ) : Parcelable, BaseBook {
     @IgnoredOnParcel
     @Ignore
-    override var variableMap: HashMap<String, String>? = null
-        get() = run {
-            initVariableMap()
-            return field
-        }
+    override var variableMap: HashMap<String, String> = GSON.fromJsonObject(variable) ?: HashMap()
 
     fun getUnreadChapterNum() = max(totalChapterNum - durChapterIndex - 1, 0)
 
@@ -62,19 +57,8 @@ data class Book(
 
     fun getDisplayIntro() = if (customIntro.isNullOrEmpty()) intro else customIntro
 
-    private fun initVariableMap() {
-        if (variableMap == null) {
-            variableMap = if (isEmpty(variable)) {
-                HashMap()
-            } else {
-                GSON.fromJsonObject(variable)
-            }
-        }
-    }
-
     override fun putVariable(key: String, value: String) {
-        initVariableMap()
-        variableMap?.put(key, value)
+        variableMap[key] = value
         variable = GSON.toJson(variableMap)
     }
 
diff --git a/app/src/main/java/io/legado/app/data/entities/SearchBook.kt b/app/src/main/java/io/legado/app/data/entities/SearchBook.kt
index 00efc0e47..69caf7c6c 100644
--- a/app/src/main/java/io/legado/app/data/entities/SearchBook.kt
+++ b/app/src/main/java/io/legado/app/data/entities/SearchBook.kt
@@ -1,7 +1,6 @@
 package io.legado.app.data.entities
 
 import android.os.Parcelable
-import android.text.TextUtils
 import androidx.room.Entity
 import androidx.room.Ignore
 import androidx.room.Index
@@ -51,25 +50,10 @@ data class SearchBook(
 
     @IgnoredOnParcel
     @Ignore
-    override var variableMap: HashMap<String, String>? = null
-        get() = run {
-            initVariableMap()
-            return field
-        }
-
-    private fun initVariableMap() {
-        variableMap?.let {
-            variableMap = if (TextUtils.isEmpty(variable)) {
-                HashMap()
-            } else {
-                GSON.fromJsonObject(variable)
-            }
-        }
-    }
+    override var variableMap: HashMap<String, String> = GSON.fromJsonObject(variable) ?: HashMap()
 
     override fun putVariable(key: String, value: String) {
-        initVariableMap()
-        variableMap?.put(key, value)
+        variableMap[key] = value
         variable = GSON.toJson(variableMap)
     }