diff --git a/.github/workflows/continuous-integration-workflow-xcode-12.yml b/.github/workflows/continuous-integration-workflow-xcode-12.yml
index 11696803..f8f96779 100644
--- a/.github/workflows/continuous-integration-workflow-xcode-12.yml
+++ b/.github/workflows/continuous-integration-workflow-xcode-12.yml
@@ -38,6 +38,10 @@ jobs:
       - name: Test NSStringUtils
         run: swift test
         working-directory: Packages/NSStringUtils
+      - name: Clean McBopomofo for testing
+        run: xcodebuild -scheme McBopomofo -configuration Debug clean
+      - name: Test McBopomofo
+        run: xcodebuild -scheme McBopomofo -configuration Debug test
       - name: Clean McBopomofo
         run: xcodebuild -scheme McBopomofo -configuration Release clean
       - name: Clean McBopomofoInstaller
diff --git a/.github/workflows/continuous-integration-workflow-xcode-latest.yml b/.github/workflows/continuous-integration-workflow-xcode-latest.yml
index 7c155bd1..a03bf5f8 100644
--- a/.github/workflows/continuous-integration-workflow-xcode-latest.yml
+++ b/.github/workflows/continuous-integration-workflow-xcode-latest.yml
@@ -38,6 +38,10 @@ jobs:
       - name: Test NSStringUtils
         run: swift test
         working-directory: Packages/NSStringUtils
+      - name: Clean McBopomofo for testing
+        run: xcodebuild -scheme McBopomofo -configuration Debug clean
+      - name: Test McBopomofo
+        run: xcodebuild -scheme McBopomofo -configuration Debug test
       - name: Clean McBopomofo
         run: xcodebuild -scheme McBopomofo -configuration Release clean
       - name: Clean McBopomofoInstaller
diff --git a/McBopomofoTests/KeyHandlerBopomofoTests.swift b/McBopomofoTests/KeyHandlerBopomofoTests.swift
index 07cfcfba..9667a4fc 100644
--- a/McBopomofoTests/KeyHandlerBopomofoTests.swift
+++ b/McBopomofoTests/KeyHandlerBopomofoTests.swift
@@ -266,17 +266,40 @@ class KeyHandlerBopomofoTests: XCTestCase {
         }
     }
 
-    func testLetter() {
-        let input = KeyHandlerInput(inputText: "A", keyCode: 0, charCode: charCode("A"), flags: .shift, isVerticalMode: false)
+    // Regression test for #292.
+    func testUppercaseLetterWhenEmpty() {
+        let input = KeyHandlerInput(inputText: "A", keyCode: KeyCode.enter.rawValue, charCode: charCode("A"), flags: [], isVerticalMode: false)
         var state: InputState = InputState.Empty()
-        handler.handle(input: input, state: state) { newState in
+        let result = handler.handle(input: input, state: state) { newState in
+            state = newState
+        } errorCallback: {
+        }
+        XCTAssertFalse(result)
+    }
+
+    // Regression test for #292.
+    func testUppercaseLetterWhenNotEmpty() {
+        var state: InputState = InputState.Empty()
+        let keys = Array("u6").map {
+            String($0)
+        }
+        for key in keys {
+            let input = KeyHandlerInput(inputText: key, keyCode: 0, charCode: charCode(key), flags: [], isVerticalMode: false)
+            handler.handle(input: input, state: state) { newState in
+                state = newState
+            } errorCallback: {
+            }
+        }
+
+        let letterInput = KeyHandlerInput(inputText: "A", keyCode: 0, charCode: charCode("A"), flags: .shift, isVerticalMode: false)
+        handler.handle(input: letterInput, state: state) { newState in
             state = newState
         } errorCallback: {
         }
 
         XCTAssertTrue(state is InputState.Inputting, "\(state)")
         if let state = state as? InputState.Inputting {
-            XCTAssertEqual(state.composingBuffer, "a")
+            XCTAssertEqual(state.composingBuffer, "一a")
         }
     }
 
diff --git a/McBopomofoTests/KeyHandlerPlainBopomofoTests.swift b/McBopomofoTests/KeyHandlerPlainBopomofoTests.swift
index 4e99ebbd..a713a179 100644
--- a/McBopomofoTests/KeyHandlerPlainBopomofoTests.swift
+++ b/McBopomofoTests/KeyHandlerPlainBopomofoTests.swift
@@ -25,15 +25,33 @@ import XCTest
 @testable import McBopomofo
 
 class KeyHandlerPlainBopomofoTests: XCTestCase {
+    var savedKeyboardLayout: Int = 0
     var handler = KeyHandler()
 
     override func setUpWithError() throws {
         LanguageModelManager.loadDataModels()
         handler = KeyHandler()
         handler.inputMode = .plainBopomofo
+
+        savedKeyboardLayout = Preferences.keyboardLayout
+
+        // Punctuation-related tests only work when the layout is Standard.
+        Preferences.keyboardLayout = KeyboardLayout.standard.rawValue
     }
 
     override func tearDownWithError() throws {
+        Preferences.keyboardLayout = savedKeyboardLayout
+    }
+
+    // Regression test for #292.
+    func testUppercaseLetterWhenEmpty() {
+        let input = KeyHandlerInput(inputText: "A", keyCode: KeyCode.enter.rawValue, charCode: charCode("A"), flags: [], isVerticalMode: false)
+        var state: InputState = InputState.Empty()
+        let result = handler.handle(input: input, state: state) { newState in
+            state = newState
+        } errorCallback: {
+        }
+        XCTAssertFalse(result)
     }
 
     func testPunctuationTable() {
diff --git a/Source/KeyHandler.mm b/Source/KeyHandler.mm
index 8209ebc5..d08bebb1 100644
--- a/Source/KeyHandler.mm
+++ b/Source/KeyHandler.mm
@@ -541,7 +541,7 @@ static NSString *const kGraphVizOutputfile = @"/tmp/McBopomofo-visualization.dot
         return YES;
     }
 
-    if ((char) charCode >= 'A' && (char) charCode <= 'Z') {
+    if ([state isKindOfClass:[InputStateNotEmpty class]] && (char) charCode >= 'A' && (char) charCode <= 'Z') {
         string letter = string("_letter_") + string(1, (char) charCode);
         if ([self _handlePunctuation:letter state:state usingVerticalMode:input.useVerticalMode stateCallback:stateCallback errorCallback:errorCallback]) {
             return YES;