diff --git a/Source/InputMethodController.swift b/Source/InputMethodController.swift
index 5ba4bac7..d51802fa 100644
--- a/Source/InputMethodController.swift
+++ b/Source/InputMethodController.swift
@@ -269,27 +269,28 @@ extension McBopomofoInputMethodController {
         let previous = state
         state = newState
 
-        if let newState = newState as? InputState.Deactivated {
+        switch newState {
+        case let newState as InputState.Deactivated:
             handle(state: newState, previous: previous, client: client)
-            // Force transition to Empty, so that when activateServer is
-            // invoked again, the controller is already in the Empty state.
             state = .Empty()
-        } else if let newState = newState as? InputState.Empty {
+        case let newState as InputState.Empty:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.EmptyIgnoringPreviousState {
+        case let newState as InputState.EmptyIgnoringPreviousState:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.Committing {
+        case let newState as InputState.Committing:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.Inputting {
+        case let newState as InputState.Inputting:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.Marking {
+        case let newState as InputState.Marking:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.ChoosingCandidate {
+        case let newState as InputState.ChoosingCandidate:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.AssociatedPhrases {
+        case let newState as InputState.AssociatedPhrases:
             handle(state: newState, previous: previous, client: client)
-        } else if let newState = newState as? InputState.Big5 {
+        case let newState as InputState.Big5:
             handle(state: newState, previous: previous, client: client)
+        default:
+            break
         }
     }
 
diff --git a/Source/PreferencesWindowController.swift b/Source/PreferencesWindowController.swift
index 9e846377..9c756eff 100644
--- a/Source/PreferencesWindowController.swift
+++ b/Source/PreferencesWindowController.swift
@@ -185,7 +185,14 @@ fileprivate let kWindowTitleHeight: CGFloat = 78
                     return newImage
                 }
 
-                menuItem.image = resize(image)
+                let resizedImage = resize(image)
+                // On newer version of macOS, the icons became black and white
+                // so we make them template images so it could look better
+                // on dark mode.
+                if #available(macOS 10.16, *) {
+                    resizedImage.isTemplate = true
+                }
+                menuItem.image = resizedImage
             }
 
             if sourceID == "com.apple.keylayout.US" {