diff --git a/lib/gui/app/app.js b/lib/gui/app/app.js
index d1b6a7a4..3fa6b64f 100644
--- a/lib/gui/app/app.js
+++ b/lib/gui/app/app.js
@@ -31,6 +31,7 @@ const store = require('./models/store')
 const packageJSON = require('../../../package.json')
 const flashState = require('./models/flash-state')
 const settings = require('./models/settings')
+// eslint-disable-next-line node/no-missing-require
 const windowProgress = require('./os/window-progress')
 const analytics = require('./modules/analytics')
 const availableDrives = require('./models/available-drives')
diff --git a/lib/gui/app/modules/image-writer.js b/lib/gui/app/modules/image-writer.js
index cc7535e7..e23eff1d 100644
--- a/lib/gui/app/modules/image-writer.js
+++ b/lib/gui/app/modules/image-writer.js
@@ -27,6 +27,7 @@ const settings = require('../models/settings')
 const flashState = require('../models/flash-state')
 const errors = require('../../../shared/errors')
 const permissions = require('../../../shared/permissions')
+// eslint-disable-next-line node/no-missing-require
 const windowProgress = require('../os/window-progress')
 const analytics = require('../modules/analytics')
 const updateLock = require('./update-lock')
diff --git a/lib/gui/app/modules/progress-status.js b/lib/gui/app/modules/progress-status.js
deleted file mode 100644
index 9aab2fec..00000000
--- a/lib/gui/app/modules/progress-status.js
+++ /dev/null
@@ -1,74 +0,0 @@
-/*
- * Copyright 2017 balena.io
- *
- * Licensed under the Apache License, Version 2.0 (the "License")
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-'use strict'
-
-const settings = require('../models/settings')
-const utils = require('../../../shared/utils')
-const units = require('../../../shared/units')
-
-/**
- * @summary Make the progress status subtitle string
- *
- * @param {Object} state - flashing metadata
- *
- * @returns {String}
- *
- * @example
- * const status = progressStatus.fromFlashState({
- *   flashing: 1,
- *   verifying: 0,
- *   successful: 0,
- *   failed: 0,
- *   percentage: 55,
- *   speed: 2049
- * })
- *
- * console.log(status)
- * // '55% Flashing'
- */
-exports.fromFlashState = (state) => {
-  const isFlashing = Boolean(state.flashing)
-  const isValidating = !isFlashing && Boolean(state.verifying)
-  const shouldValidate = settings.get('validateWriteOnSuccess')
-  const shouldUnmount = settings.get('unmountOnSuccess')
-
-  if (state.percentage === utils.PERCENTAGE_MINIMUM && !state.speed) {
-    if (isValidating) {
-      return 'Validating...'
-    }
-
-    return 'Starting...'
-  } else if (state.percentage === utils.PERCENTAGE_MAXIMUM) {
-    if ((isValidating || !shouldValidate) && shouldUnmount) {
-      return 'Unmounting...'
-    }
-
-    return 'Finishing...'
-  } else if (isFlashing) {
-    // eslint-disable-next-line no-eq-null
-    if (state.percentage != null) {
-      return `${state.percentage}% Flashing`
-    }
-    return `${units.bytesToClosestUnit(state.position)} flashed`
-  } else if (isValidating) {
-    return `${state.percentage}% Validating`
-  } else if (!isFlashing && !isValidating) {
-    return 'Failed'
-  }
-
-  throw new Error(`Invalid state: ${JSON.stringify(state)}`)
-}
diff --git a/lib/gui/app/modules/progress-status.ts b/lib/gui/app/modules/progress-status.ts
new file mode 100644
index 00000000..789bc815
--- /dev/null
+++ b/lib/gui/app/modules/progress-status.ts
@@ -0,0 +1,80 @@
+/*
+ * Copyright 2017 balena.io
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License")
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { bytesToClosestUnit } from '../../../shared/units';
+import * as settings from '../models/settings';
+
+export interface FlashState {
+	flashing: number;
+	verifying: number;
+	successful: number;
+	failed: number;
+	percentage?: number;
+	speed: number;
+	position: number;
+}
+
+/**
+ * @summary Make the progress status subtitle string
+ *
+ * @param {Object} state - flashing metadata
+ *
+ * @returns {String}
+ *
+ * @example
+ * const status = progressStatus.fromFlashState({
+ *   flashing: 1,
+ *   verifying: 0,
+ *   successful: 0,
+ *   failed: 0,
+ *   percentage: 55,
+ *   speed: 2049
+ * })
+ *
+ * console.log(status)
+ * // '55% Flashing'
+ */
+export function fromFlashState(state: FlashState): string {
+	const isFlashing = Boolean(state.flashing);
+	const isValidating = !isFlashing && Boolean(state.verifying);
+	const shouldValidate = settings.get('validateWriteOnSuccess');
+	const shouldUnmount = settings.get('unmountOnSuccess');
+
+	if (state.percentage === 0 && !state.speed) {
+		if (isValidating) {
+			return 'Validating...';
+		}
+
+		return 'Starting...';
+	} else if (state.percentage === 100) {
+		if ((isValidating || !shouldValidate) && shouldUnmount) {
+			return 'Unmounting...';
+		}
+
+		return 'Finishing...';
+	} else if (isFlashing) {
+		if (state.percentage != null) {
+			return `${state.percentage}% Flashing`;
+		}
+		return `${bytesToClosestUnit(state.position)} flashed`;
+	} else if (isValidating) {
+		return `${state.percentage}% Validating`;
+	} else if (!isFlashing && !isValidating) {
+		return 'Failed';
+	}
+
+	throw new Error(`Invalid state: ${JSON.stringify(state)}`);
+}
diff --git a/lib/gui/app/os/window-progress.js b/lib/gui/app/os/window-progress.js
deleted file mode 100644
index 915cc9fe..00000000
--- a/lib/gui/app/os/window-progress.js
+++ /dev/null
@@ -1,114 +0,0 @@
-/*
- * Copyright 2016 balena.io
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-'use strict'
-
-const electron = require('electron')
-const utils = require('../../../shared/utils')
-const progressStatus = require('../modules/progress-status')
-
-/**
- * @summary The title of the main window upon program launch
- * @type {String}
- * @private
- * @constant
- */
-const INITIAL_TITLE = document.title
-
-/**
- * @summary Make the full window status title
- * @private
- *
- * @param {Object} state - flash state object
- *
- * @returns {String}
- *
- * @example
- * const title = getWindowTitle({
- *   flashing: 1,
- *   validating: 0,
- *   successful: 0,
- *   failed: 0,
- *   percentage: 55,
- *   speed: 2049
- * });
- *
- * console.log(title);
- * // 'Etcher \u2013 55% Flashing'
- */
-const getWindowTitle = (state) => {
-  if (state) {
-    const subtitle = progressStatus.fromFlashState(state)
-    const DASH_UNICODE_CHAR = '\u2013'
-    return `${INITIAL_TITLE} ${DASH_UNICODE_CHAR} ${subtitle}`
-  }
-
-  return INITIAL_TITLE
-}
-
-/**
- * @summary A reference to the current renderer Electron window
- * @type {Object}
- * @protected
- *
- * @description
- * We expose this property to `this` for testability purposes.
- */
-exports.currentWindow = electron.remote.getCurrentWindow()
-
-/**
- * @summary Set operating system window progress
- * @function
- * @public
- *
- * @description
- * Show progress inline in operating system task bar
- *
- * @param {Number} state - flash state object
- *
- * @example
- * windowProgress.set({
- *   flashing: 1,
- *   validating: 0,
- *   successful: 0,
- *   failed: 0,
- *   percentage: 55,
- *   speed: 2049
- * })
- */
-exports.set = (state) => {
-  // eslint-disable-next-line no-eq-null
-  if (state.percentage != null) {
-    exports.currentWindow.setProgressBar(utils.percentageToFloat(state.percentage))
-  }
-  exports.currentWindow.setTitle(getWindowTitle(state))
-}
-
-/**
- * @summary Clear the window progress bar
- * @function
- * @public
- *
- * @example
- * windowProgress.clear();
- */
-exports.clear = () => {
-  // Passing 0 or null/undefined doesn't work.
-  const ELECTRON_PROGRESS_BAR_RESET_VALUE = -1
-
-  exports.currentWindow.setProgressBar(ELECTRON_PROGRESS_BAR_RESET_VALUE)
-  exports.currentWindow.setTitle(getWindowTitle(null))
-}
diff --git a/lib/gui/app/os/window-progress.ts b/lib/gui/app/os/window-progress.ts
new file mode 100644
index 00000000..443fee7e
--- /dev/null
+++ b/lib/gui/app/os/window-progress.ts
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2016 balena.io
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as electron from 'electron';
+
+import { percentageToFloat } from '../../../shared/utils';
+import { FlashState, fromFlashState } from '../modules/progress-status';
+
+/**
+ * @summary The title of the main window upon program launch
+ */
+const INITIAL_TITLE = document.title;
+
+/**
+ * @summary Make the full window status title
+ */
+function getWindowTitle(state?: FlashState) {
+	if (state) {
+		return `${INITIAL_TITLE} – ${fromFlashState(state)}`;
+	}
+	return INITIAL_TITLE;
+}
+
+/**
+ * @summary A reference to the current renderer Electron window
+ *
+ * @description
+ * We expose this property to `this` for testability purposes.
+ */
+export const currentWindow = electron.remote.getCurrentWindow();
+
+/**
+ * @summary Set operating system window progress
+ *
+ * @description
+ * Show progress inline in operating system task bar
+ */
+export function set(state: FlashState) {
+	if (state.percentage != null) {
+		exports.currentWindow.setProgressBar(percentageToFloat(state.percentage));
+	}
+	exports.currentWindow.setTitle(getWindowTitle(state));
+}
+
+/**
+ * @summary Clear the window progress bar
+ */
+export function clear() {
+	// Passing 0 or null/undefined doesn't work.
+	exports.currentWindow.setProgressBar(-1);
+	exports.currentWindow.setTitle(getWindowTitle(undefined));
+}
diff --git a/lib/gui/app/pages/main/Flash.tsx b/lib/gui/app/pages/main/Flash.tsx
index 31ca0710..ce605a95 100644
--- a/lib/gui/app/pages/main/Flash.tsx
+++ b/lib/gui/app/pages/main/Flash.tsx
@@ -145,7 +145,8 @@ const getProgressButtonLabel = () => {
 		return 'Flash!';
 	}
 
-	return progressStatus.fromFlashState(flashState.getFlashState());
+	// TODO: no any
+	return progressStatus.fromFlashState(flashState.getFlashState() as any);
 };
 
 const formatSeconds = (totalSeconds: number) => {
diff --git a/tests/gui/modules/progress-status.spec.js b/tests/gui/modules/progress-status.spec.js
index 3eb38e69..42e3e95b 100644
--- a/tests/gui/modules/progress-status.spec.js
+++ b/tests/gui/modules/progress-status.spec.js
@@ -2,6 +2,7 @@
 
 const m = require('mochainon')
 const settings = require('../../../lib/gui/app/models/settings')
+// eslint-disable-next-line node/no-missing-require
 const progressStatus = require('../../../lib/gui/app/modules/progress-status')
 
 describe('Browser: progressStatus', function () {
diff --git a/tests/gui/os/window-progress.spec.js b/tests/gui/os/window-progress.spec.js
index 84321953..9893a6fc 100644
--- a/tests/gui/os/window-progress.spec.js
+++ b/tests/gui/os/window-progress.spec.js
@@ -17,6 +17,7 @@
 'use strict'
 
 const m = require('mochainon')
+// eslint-disable-next-line node/no-missing-require
 const windowProgress = require('../../../lib/gui/app/os/window-progress')
 
 describe('Browser: WindowProgress', function () {