diff --git a/src/CharWidth.ts b/src/CharWidth.ts
index fd6ac55f..43cd948e 100644
--- a/src/CharWidth.ts
+++ b/src/CharWidth.ts
@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { fill } from './core/TypedArrayUtils';
+import { fill } from './common/TypedArrayUtils';
 
 export const wcwidth = (function(opts: {nul: number, control: number}): (ucs: number) => number {
   // extracted from https://www.cl.cam.ac.uk/%7Emgk25/ucs/wcwidth.c
diff --git a/src/common/TypedArrayUtils.test.ts b/src/common/TypedArrayUtils.test.ts
new file mode 100644
index 00000000..69a62abc
--- /dev/null
+++ b/src/common/TypedArrayUtils.test.ts
@@ -0,0 +1,89 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+import { assert } from 'chai';
+import { fillFallback } from './TypedArrayUtils';
+
+type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
+  | Int8Array | Int16Array | Int32Array
+  | Float32Array | Float64Array;
+
+describe('polyfill conformance tests', function(): void {
+
+  function deepEquals(a: TypedArray, b: TypedArray): void {
+    assert.equal(a.length, b.length);
+    for (let i = 0; i < a.length; ++i) {
+      assert.equal(a[i], b[i]);
+    }
+  }
+
+  describe('TypedArray.fill', function(): void {
+    it('should work with all typed array types', function(): void {
+      const u81 = new Uint8Array(5);
+      const u82 = new Uint8Array(5);
+      deepEquals(fillFallback(u81, 2), u82.fill(2));
+      deepEquals(fillFallback(u81, -1), u82.fill(-1));
+      const u161 = new Uint16Array(5);
+      const u162 = new Uint16Array(5);
+      deepEquals(fillFallback(u161, 2), u162.fill(2));
+      deepEquals(fillFallback(u161, 65535), u162.fill(65535));
+      deepEquals(fillFallback(u161, -1), u162.fill(-1));
+      const u321 = new Uint32Array(5);
+      const u322 = new Uint32Array(5);
+      deepEquals(fillFallback(u321, 2), u322.fill(2));
+      deepEquals(fillFallback(u321, 65537), u322.fill(65537));
+      deepEquals(fillFallback(u321, -1), u322.fill(-1));
+      const i81 = new Int8Array(5);
+      const i82 = new Int8Array(5);
+      deepEquals(fillFallback(i81, 2), i82.fill(2));
+      deepEquals(fillFallback(i81, -1), i82.fill(-1));
+      const i161 = new Int16Array(5);
+      const i162 = new Int16Array(5);
+      deepEquals(fillFallback(i161, 2), i162.fill(2));
+      deepEquals(fillFallback(i161, 65535), i162.fill(65535));
+      deepEquals(fillFallback(i161, -1), i162.fill(-1));
+      const i321 = new Int32Array(5);
+      const i322 = new Int32Array(5);
+      deepEquals(fillFallback(i321, 2), i322.fill(2));
+      deepEquals(fillFallback(i321, 65537), i322.fill(65537));
+      deepEquals(fillFallback(i321, -1), i322.fill(-1));
+      const f321 = new Float32Array(5);
+      const f322 = new Float32Array(5);
+      deepEquals(fillFallback(f321, 1.2345), f322.fill(1.2345));
+      const f641 = new Float64Array(5);
+      const f642 = new Float64Array(5);
+      deepEquals(fillFallback(f641, 1.2345), f642.fill(1.2345));
+      const u8Clamped1 = new Uint8ClampedArray(5);
+      const u8Clamped2 = new Uint8ClampedArray(5);
+      deepEquals(fillFallback(u8Clamped1, 2), u8Clamped2.fill(2));
+      deepEquals(fillFallback(u8Clamped1, 257), u8Clamped2.fill(257));
+    });
+    it('start offset', function(): void {
+      for (let i = -2; i < 10; ++i) {
+        const u81 = new Uint8Array(5);
+        const u83 = new Uint8Array(5);
+        deepEquals(fillFallback(u81, 2, i), u83.fill(2, i));
+        deepEquals(fillFallback(u81, -1, i), u83.fill(-1, i));
+      }
+    });
+    it('end offset', function(): void {
+      for (let i = -2; i < 10; ++i) {
+        const u81 = new Uint8Array(5);
+        const u83 = new Uint8Array(5);
+        deepEquals(fillFallback(u81, 2, 0, i), u83.fill(2, 0, i));
+        deepEquals(fillFallback(u81, -1, 0, i), u83.fill(-1, 0, i));
+      }
+    });
+    it('start/end offset', function(): void {
+      for (let i = -2; i < 10; ++i) {
+        for (let j = -2; j < 10; ++j) {
+          const u81 = new Uint8Array(5);
+          const u83 = new Uint8Array(5);
+          deepEquals(fillFallback(u81, 2, i, j), u83.fill(2, i, j));
+          deepEquals(fillFallback(u81, -1, i, j), u83.fill(-1, i, j));
+        }
+      }
+    });
+  });
+});
diff --git a/src/core/TypedArrayUtils.ts b/src/common/TypedArrayUtils.ts
similarity index 73%
rename from src/core/TypedArrayUtils.ts
rename to src/common/TypedArrayUtils.ts
index 56e9d7b0..6e1a3630 100644
--- a/src/core/TypedArrayUtils.ts
+++ b/src/common/TypedArrayUtils.ts
@@ -12,11 +12,15 @@ type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
   | Int8Array | Int16Array | Int32Array
   | Float32Array | Float64Array;
 
-export function fill(array: TypedArray, value: number, start: number = 0, end?: number | undefined): TypedArray {
+export function fill<T extends TypedArray>(array: T, value: number, start?: number, end?: number): T {
   // all modern engines that support .fill
   if (array.fill) {
-    return array.fill(value, start, end);
+    return array.fill(value, start, end) as T;
   }
+  return fillFallback(array, value, start, end);
+}
+
+export function fillFallback<T extends TypedArray>(array: T, value: number, start: number = 0, end: number = array.length): T {
   // safari and IE 11
   // since IE 11 does not support Array.prototype.fill either
   // we cannot use the suggested polyfill from MDN
@@ -25,9 +29,6 @@ export function fill(array: TypedArray, value: number, start: number = 0, end?:
     return array;
   }
   start = (array.length + start) % array.length;
-  if (end === undefined) {
-    end = array.length;
-  }
   if (end >= array.length) {
     end = array.length;
   } else {
diff --git a/src/core/TypedArrayUtils.test.ts b/src/core/TypedArrayUtils.test.ts
deleted file mode 100644
index ef86d314..00000000
--- a/src/core/TypedArrayUtils.test.ts
+++ /dev/null
@@ -1,158 +0,0 @@
-/**
- * Copyright (c) 2018 The xterm.js authors. All rights reserved.
- * @license MIT
- */
-import { assert } from 'chai';
-import { fill } from './TypedArrayUtils';
-
-type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
-  | Int8Array | Int16Array | Int32Array
-  | Float32Array | Float64Array;
-
-// we explicitly test against the looping version in the test cases
-function loopFill(array: TypedArray, value: number, start: number = 0, end?: number | undefined): TypedArray {
-  if (start >= array.length) {
-    return array;
-  }
-  start = (array.length + start) % array.length;
-  if (end === undefined) {
-    end = array.length;
-  }
-  if (end >= array.length) {
-    end = array.length;
-  } else {
-    end = (array.length + end) % array.length;
-  }
-  for (let i = start; i < end; ++i) {
-    array[i] = value;
-  }
-  return array;
-}
-
-describe('polyfill conformance tests', function(): void {
-
-  function deepEquals(a: TypedArray, b: TypedArray): void {
-    assert.equal(a.length, b.length);
-    for (let i = 0; i < a.length; ++i) {
-      assert.equal(a[i], b[i]);
-    }
-  }
-
-  describe('TypedArray.fill', function(): void {
-    it('should work with all typed array types', function(): void {
-      const u81 = new Uint8Array(5);
-      const u82 = new Uint8Array(5);
-      deepEquals(fill(u81, 2), u82.fill(2));
-      deepEquals(fill(u81, -1), u82.fill(-1));
-      const u161 = new Uint16Array(5);
-      const u162 = new Uint16Array(5);
-      deepEquals(fill(u161, 2), u162.fill(2));
-      deepEquals(fill(u161, 65535), u162.fill(65535));
-      deepEquals(fill(u161, -1), u162.fill(-1));
-      const u321 = new Uint32Array(5);
-      const u322 = new Uint32Array(5);
-      deepEquals(fill(u321, 2), u322.fill(2));
-      deepEquals(fill(u321, 65537), u322.fill(65537));
-      deepEquals(fill(u321, -1), u322.fill(-1));
-      const i81 = new Int8Array(5);
-      const i82 = new Int8Array(5);
-      deepEquals(fill(i81, 2), i82.fill(2));
-      deepEquals(fill(i81, -1), i82.fill(-1));
-      const i161 = new Int16Array(5);
-      const i162 = new Int16Array(5);
-      deepEquals(fill(i161, 2), i162.fill(2));
-      deepEquals(fill(i161, 65535), i162.fill(65535));
-      deepEquals(fill(i161, -1), i162.fill(-1));
-      const i321 = new Int32Array(5);
-      const i322 = new Int32Array(5);
-      deepEquals(fill(i321, 2), i322.fill(2));
-      deepEquals(fill(i321, 65537), i322.fill(65537));
-      deepEquals(fill(i321, -1), i322.fill(-1));
-      const f321 = new Float32Array(5);
-      const f322 = new Float32Array(5);
-      deepEquals(fill(f321, 1.2345), f322.fill(1.2345));
-      const f641 = new Float64Array(5);
-      const f642 = new Float64Array(5);
-      deepEquals(fill(f641, 1.2345), f642.fill(1.2345));
-      const u8Clamped1 = new Uint8ClampedArray(5);
-      const u8Clamped2 = new Uint8ClampedArray(5);
-      deepEquals(fill(u8Clamped1, 2), u8Clamped2.fill(2));
-      deepEquals(fill(u8Clamped1, 257), u8Clamped2.fill(257));
-    });
-    it('should work with all typed array types - explicit looping', function(): void {
-      const u81 = new Uint8Array(5);
-      const u82 = new Uint8Array(5);
-      deepEquals(loopFill(u81, 2), u82.fill(2));
-      deepEquals(loopFill(u81, -1), u82.fill(-1));
-      const u161 = new Uint16Array(5);
-      const u162 = new Uint16Array(5);
-      deepEquals(loopFill(u161, 2), u162.fill(2));
-      deepEquals(loopFill(u161, 65535), u162.fill(65535));
-      deepEquals(loopFill(u161, -1), u162.fill(-1));
-      const u321 = new Uint32Array(5);
-      const u322 = new Uint32Array(5);
-      deepEquals(loopFill(u321, 2), u322.fill(2));
-      deepEquals(loopFill(u321, 65537), u322.fill(65537));
-      deepEquals(loopFill(u321, -1), u322.fill(-1));
-      const i81 = new Int8Array(5);
-      const i82 = new Int8Array(5);
-      deepEquals(loopFill(i81, 2), i82.fill(2));
-      deepEquals(loopFill(i81, -1), i82.fill(-1));
-      const i161 = new Int16Array(5);
-      const i162 = new Int16Array(5);
-      deepEquals(loopFill(i161, 2), i162.fill(2));
-      deepEquals(loopFill(i161, 65535), i162.fill(65535));
-      deepEquals(loopFill(i161, -1), i162.fill(-1));
-      const i321 = new Int32Array(5);
-      const i322 = new Int32Array(5);
-      deepEquals(loopFill(i321, 2), i322.fill(2));
-      deepEquals(loopFill(i321, 65537), i322.fill(65537));
-      deepEquals(loopFill(i321, -1), i322.fill(-1));
-      const f321 = new Float32Array(5);
-      const f322 = new Float32Array(5);
-      deepEquals(loopFill(f321, 1.2345), f322.fill(1.2345));
-      const f641 = new Float64Array(5);
-      const f642 = new Float64Array(5);
-      deepEquals(loopFill(f641, 1.2345), f642.fill(1.2345));
-      const u8Clamped1 = new Uint8ClampedArray(5);
-      const u8Clamped2 = new Uint8ClampedArray(5);
-      deepEquals(loopFill(u8Clamped1, 2), u8Clamped2.fill(2));
-      deepEquals(loopFill(u8Clamped1, 257), u8Clamped2.fill(257));
-    });
-    it('start offset', function(): void {
-      for (let i = -2; i < 10; ++i) {
-        const u81 = new Uint8Array(5);
-        const u82 = new Uint8Array(5);
-        const u83 = new Uint8Array(5);
-        deepEquals(fill(u81, 2, i), u83.fill(2, i));
-        deepEquals(fill(u81, -1, i), u83.fill(-1, i));
-        deepEquals(loopFill(u82, 2, i), u83.fill(2, i));
-        deepEquals(loopFill(u82, -1, i), u83.fill(-1, i));
-      }
-    });
-    it('end offset', function(): void {
-      for (let i = -2; i < 10; ++i) {
-        const u81 = new Uint8Array(5);
-        const u82 = new Uint8Array(5);
-        const u83 = new Uint8Array(5);
-        deepEquals(fill(u81, 2, 0, i), u83.fill(2, 0, i));
-        deepEquals(fill(u81, -1, 0, i), u83.fill(-1, 0, i));
-        deepEquals(loopFill(u82, 2, 0, i), u83.fill(2, 0, i));
-        deepEquals(loopFill(u82, -1, 0, i), u83.fill(-1, 0, i));
-      }
-    });
-    it('start/end offset', function(): void {
-      for (let i = -2; i < 10; ++i) {
-        for (let j = -2; j < 10; ++j) {
-          const u81 = new Uint8Array(5);
-          const u82 = new Uint8Array(5);
-          const u83 = new Uint8Array(5);
-          deepEquals(fill(u81, 2, i, j), u83.fill(2, i, j));
-          deepEquals(fill(u81, -1, i, j), u83.fill(-1, i, j));
-          deepEquals(loopFill(u82, 2, i, j), u83.fill(2, i, j));
-          deepEquals(loopFill(u82, -1, i, j), u83.fill(-1, i, j));
-        }
-      }
-    });
-  });
-});