diff --git a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
index f050521a..24744004 100644
--- a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
+++ b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
@@ -111,10 +111,7 @@ class ctlInputMethod: IMKInputController {
     keyHandler.clear()  // 這句不要砍，因為後面 handle State.Empty() 不一定執行。
     keyHandler.ensureParser()
 
-    if #available(macOS 10.13, *) {
-    } else {
-      mgrPrefs.useIMKCandidateWindow = false  // 防呆。macOS 10.11 用 IMK 選字窗會崩潰。
-    }
+    mgrPrefs.fixOddPreferences()
 
     if isASCIIMode {
       if mgrPrefs.disableShiftTogglingAlphanumericalMode {
diff --git a/Source/Modules/IMEModules/mgrPrefs.swift b/Source/Modules/IMEModules/mgrPrefs.swift
index 59c8dd3a..fe2aaa0c 100644
--- a/Source/Modules/IMEModules/mgrPrefs.swift
+++ b/Source/Modules/IMEModules/mgrPrefs.swift
@@ -664,6 +664,21 @@ public enum mgrPrefs {
   static var usingHotKeyCurrencyNumerals: Bool
 }
 
+// MARK: Auto parameter fix procedures, executed everytime on ctlInputMethod.activateServer().
+
+extension mgrPrefs {
+  static func fixOddPreferences() {
+    // 防呆。macOS 10.11 用 IMK 選字窗會崩潰。
+    if #unavailable(macOS 10.13) { mgrPrefs.useIMKCandidateWindow = false }
+    if #unavailable(macOS 10.15) {
+      handleDefaultCandidateFontsByLangIdentifier = false
+      shouldAlwaysUseShiftKeyAccommodation = false
+      disableShiftTogglingAlphanumericalMode = false
+      togglingAlphanumericalModeWithLShift = false
+    }
+  }
+}
+
 // MARK: Snapshot Extension
 
 var snapshot: [String: Any]?