diff --git a/src/InputHandler.test.ts b/src/InputHandler.test.ts
index 37a54e39a..5a3dc2b5a 100644
--- a/src/InputHandler.test.ts
+++ b/src/InputHandler.test.ts
@@ -4,7 +4,7 @@
  */
 
 import { assert, expect } from 'chai';
-import { InputHandler } from './InputHandler';
+import { InputHandler } from './common/InputHandler';
 import { TestTerminal } from './TestUtils.test';
 import { Terminal } from './Terminal';
 import { IBufferLine, IAttributeData } from 'common/Types';
diff --git a/src/Terminal.ts b/src/Terminal.ts
index e3af555b7..61c997bd0 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -27,7 +27,7 @@ import { CompositionHelper } from 'browser/input/CompositionHelper';
 import { Viewport } from 'browser/Viewport';
 import { rightClickHandler, moveTextAreaUnderMouseCursor, handlePasteEvent, copyHandler, paste } from 'browser/Clipboard';
 import { C0 } from 'common/data/EscapeSequences';
-import { InputHandler, WindowsOptionsReportType } from './InputHandler';
+import { InputHandler, WindowsOptionsReportType } from './common/InputHandler';
 import { Renderer } from 'browser/renderer/Renderer';
 import { Linkifier } from 'browser/Linkifier';
 import { SelectionService } from 'browser/services/SelectionService';
diff --git a/src/Types.d.ts b/src/Types.d.ts
index 2f57e99c0..05c89e158 100644
--- a/src/Types.d.ts
+++ b/src/Types.d.ts
@@ -23,91 +23,6 @@ export interface ICompositionHelper {
   keydown(ev: KeyboardEvent): boolean;
 }
 
-/**
- * Calls the parser and handles actions generated by the parser.
- */
-export interface IInputHandler {
-  onTitleChange: IEvent<string>;
-  onRequestScroll: IEvent<IAttributeData, boolean | void>;
-
-  parse(data: string | Uint8Array): void;
-  print(data: Uint32Array, start: number, end: number): void;
-
-  /** C0 BEL */ bell(): void;
-  /** C0 LF */ lineFeed(): void;
-  /** C0 CR */ carriageReturn(): void;
-  /** C0 BS */ backspace(): void;
-  /** C0 HT */ tab(): void;
-  /** C0 SO */ shiftOut(): void;
-  /** C0 SI */ shiftIn(): void;
-
-  /** CSI @ */ insertChars(params: IParams): void;
-  /** CSI SP @ */ scrollLeft(params: IParams): void;
-  /** CSI A */ cursorUp(params: IParams): void;
-  /** CSI SP A */ scrollRight(params: IParams): void;
-  /** CSI B */ cursorDown(params: IParams): void;
-  /** CSI C */ cursorForward(params: IParams): void;
-  /** CSI D */ cursorBackward(params: IParams): void;
-  /** CSI E */ cursorNextLine(params: IParams): void;
-  /** CSI F */ cursorPrecedingLine(params: IParams): void;
-  /** CSI G */ cursorCharAbsolute(params: IParams): void;
-  /** CSI H */ cursorPosition(params: IParams): void;
-  /** CSI I */ cursorForwardTab(params: IParams): void;
-  /** CSI J */ eraseInDisplay(params: IParams): void;
-  /** CSI K */ eraseInLine(params: IParams): void;
-  /** CSI L */ insertLines(params: IParams): void;
-  /** CSI M */ deleteLines(params: IParams): void;
-  /** CSI P */ deleteChars(params: IParams): void;
-  /** CSI S */ scrollUp(params: IParams): void;
-  /** CSI T */ scrollDown(params: IParams, collect?: string): void;
-  /** CSI X */ eraseChars(params: IParams): void;
-  /** CSI Z */ cursorBackwardTab(params: IParams): void;
-  /** CSI ` */ charPosAbsolute(params: IParams): void;
-  /** CSI a */ hPositionRelative(params: IParams): void;
-  /** CSI b */ repeatPrecedingCharacter(params: IParams): void;
-  /** CSI c */ sendDeviceAttributesPrimary(params: IParams): void;
-  /** CSI > c */ sendDeviceAttributesSecondary(params: IParams): void;
-  /** CSI d */ linePosAbsolute(params: IParams): void;
-  /** CSI e */ vPositionRelative(params: IParams): void;
-  /** CSI f */ hVPosition(params: IParams): void;
-  /** CSI g */ tabClear(params: IParams): void;
-  /** CSI h */ setMode(params: IParams, collect?: string): void;
-  /** CSI l */ resetMode(params: IParams, collect?: string): void;
-  /** CSI m */ charAttributes(params: IParams): void;
-  /** CSI n */ deviceStatus(params: IParams, collect?: string): void;
-  /** CSI p */ softReset(params: IParams, collect?: string): void;
-  /** CSI q */ setCursorStyle(params: IParams, collect?: string): void;
-  /** CSI r */ setScrollRegion(params: IParams, collect?: string): void;
-  /** CSI s */ saveCursor(params: IParams): void;
-  /** CSI u */ restoreCursor(params: IParams): void;
-  /** CSI ' } */ insertColumns(params: IParams): void;
-  /** CSI ' ~ */ deleteColumns(params: IParams): void;
-  /** OSC 0
-      OSC 2 */ setTitle(data: string): void;
-  /** ESC E */ nextLine(): void;
-  /** ESC = */ keypadApplicationMode(): void;
-  /** ESC > */ keypadNumericMode(): void;
-  /** ESC % G
-      ESC % @ */ selectDefaultCharset(): void;
-  /** ESC ( C
-      ESC ) C
-      ESC * C
-      ESC + C
-      ESC - C
-      ESC . C
-      ESC / C */ selectCharset(collectAndFlag: string): void;
-  /** ESC D */ index(): void;
-  /** ESC H */ tabSet(): void;
-  /** ESC M */ reverseIndex(): void;
-  /** ESC c */ fullReset(): void;
-  /** ESC n
-      ESC o
-      ESC |
-      ESC }
-      ESC ~ */ setgLevel(level: number): void;
-  /** ESC # 8 */ screenAlignmentPattern(): void;
-}
-
 export interface ITerminal extends IPublicTerminal, IElementAccessor, IBufferAccessor, ILinkifierAccessor {
   screenElement: HTMLElement;
   browser: IBrowser;
diff --git a/src/InputHandler.ts b/src/common/InputHandler.ts
similarity index 99%
rename from src/InputHandler.ts
rename to src/common/InputHandler.ts
index 61ef55463..70ec8859c 100644
--- a/src/InputHandler.ts
+++ b/src/common/InputHandler.ts
@@ -4,7 +4,7 @@
  * @license MIT
  */
 
-import { IInputHandler } from './Types';
+import { IInputHandler, IAttributeData, IDisposable, IWindowOptions } from 'common/Types';
 import { C0, C1 } from 'common/data/EscapeSequences';
 import { CHARSETS, DEFAULT_CHARSET } from 'common/data/Charsets';
 import { EscapeSequenceParser } from 'common/parser/EscapeSequenceParser';
@@ -17,7 +17,6 @@ import { IParsingState, IDcsHandler, IEscapeSequenceParser, IParams, IFunctionId
 import { NULL_CELL_CODE, NULL_CELL_WIDTH, Attributes, FgFlags, BgFlags, Content } from 'common/buffer/Constants';
 import { CellData } from 'common/buffer/CellData';
 import { AttributeData } from 'common/buffer/AttributeData';
-import { IAttributeData, IDisposable, IWindowOptions } from 'common/Types';
 import { ICoreService, IBufferService, IOptionsService, ILogService, IDirtyRowService, ICoreMouseService, ICharsetService, IUnicodeService } from 'common/services/Services';
 import { OscHandler } from 'common/parser/OscParser';
 import { DcsHandler } from 'common/parser/DcsParser';
@@ -504,7 +503,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     const wraparoundMode = this._coreService.decPrivateModes.wraparound;
     const insertMode = this._coreService.modes.insertMode;
     const curAttr = this._curAttrData;
-    let bufferRow = buffer.lines.get(buffer.y + buffer.ybase);
+    let bufferRow = buffer.lines.get(buffer.y + buffer.ybase)!;
 
     this._dirtyRowService.markDirty(buffer.y);
 
@@ -568,10 +567,10 @@ export class InputHandler extends Disposable implements IInputHandler {
             }
             // The line already exists (eg. the initial viewport), mark it as a
             // wrapped line
-            buffer.lines.get(buffer.y).isWrapped = true;
+            buffer.lines.get(buffer.y)!.isWrapped = true;
           }
           // row changed, get it again
-          bufferRow = buffer.lines.get(buffer.y + buffer.ybase);
+          bufferRow = buffer.lines.get(buffer.y + buffer.ybase)!;
         } else {
           buffer.x = cols - 1;
           if (chWidth === 2) {
@@ -1037,7 +1036,7 @@ export class InputHandler extends Disposable implements IInputHandler {
    * @param end   end - 1 is last erased cell
    */
   private _eraseInBufferLine(y: number, start: number, end: number, clearWrap: boolean = false): void {
-    const line = this._bufferService.buffer.lines.get(this._bufferService.buffer.ybase + y);
+    const line = this._bufferService.buffer.lines.get(this._bufferService.buffer.ybase + y)!;
     line.replaceCells(
       start,
       end,
@@ -1055,7 +1054,7 @@ export class InputHandler extends Disposable implements IInputHandler {
    * @param y row index
    */
   private _resetBufferLine(y: number): void {
-    const line = this._bufferService.buffer.lines.get(this._bufferService.buffer.ybase + y);
+    const line = this._bufferService.buffer.lines.get(this._bufferService.buffer.ybase + y)!;
     line.fill(this._bufferService.buffer.getNullCell(this._eraseAttrData()));
     line.isWrapped = false;
   }
@@ -1104,7 +1103,7 @@ export class InputHandler extends Disposable implements IInputHandler {
         this._eraseInBufferLine(j, 0, this._bufferService.buffer.x + 1, true);
         if (this._bufferService.buffer.x + 1 >= this._bufferService.cols) {
           // Deleted entire previous line. This next line can no longer be wrapped.
-          this._bufferService.buffer.lines.get(j + 1).isWrapped = false;
+          this._bufferService.buffer.lines.get(j + 1)!.isWrapped = false;
         }
         while (j--) {
           this._resetBufferLine(j);
@@ -1356,7 +1355,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     }
     const param = params.params[0] || 1;
     for (let y = buffer.scrollTop; y <= buffer.scrollBottom; ++y) {
-      const line = buffer.lines.get(buffer.ybase + y);
+      const line = buffer.lines.get(buffer.ybase + y)!;
       line.deleteCells(0, param, buffer.getNullCell(this._eraseAttrData()), this._eraseAttrData());
       line.isWrapped = false;
     }
@@ -1389,7 +1388,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     }
     const param = params.params[0] || 1;
     for (let y = buffer.scrollTop; y <= buffer.scrollBottom; ++y) {
-      const line = buffer.lines.get(buffer.ybase + y);
+      const line = buffer.lines.get(buffer.ybase + y)!;
       line.insertCells(0, param, buffer.getNullCell(this._eraseAttrData()), this._eraseAttrData());
       line.isWrapped = false;
     }
@@ -1412,7 +1411,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     }
     const param = params.params[0] || 1;
     for (let y = buffer.scrollTop; y <= buffer.scrollBottom; ++y) {
-      const line = this._bufferService.buffer.lines.get(buffer.ybase + y);
+      const line = this._bufferService.buffer.lines.get(buffer.ybase + y)!;
       line.insertCells(buffer.x, param, buffer.getNullCell(this._eraseAttrData()), this._eraseAttrData());
       line.isWrapped = false;
     }
@@ -1435,7 +1434,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     }
     const param = params.params[0] || 1;
     for (let y = buffer.scrollTop; y <= buffer.scrollBottom; ++y) {
-      const line = buffer.lines.get(buffer.ybase + y);
+      const line = buffer.lines.get(buffer.ybase + y)!;
       line.deleteCells(buffer.x, param, buffer.getNullCell(this._eraseAttrData()), this._eraseAttrData());
       line.isWrapped = false;
     }
@@ -2064,7 +2063,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     do {
       accu[advance + cSpace] = params.params[pos + advance];
       if (params.hasSubParams(pos + advance)) {
-        const subparams = params.getSubParams(pos + advance);
+        const subparams = params.getSubParams(pos + advance)!;
         let i = 0;
         do {
           if (accu[1] === 5) {
@@ -2519,12 +2518,12 @@ export class InputHandler extends Disposable implements IInputHandler {
       case 23:  // PopTitle
         if (second === 0 || second === 2) {
           if (this._windowTitleStack.length) {
-            this.setTitle(this._windowTitleStack.pop());
+            this.setTitle(this._windowTitleStack.pop()!);
           }
         }
         if (second === 0 || second === 1) {
           if (this._iconNameStack.length) {
-            this.setIconName(this._iconNameStack.pop());
+            this.setIconName(this._iconNameStack.pop()!);
           }
         }
         break;
@@ -2788,8 +2787,11 @@ export class InputHandler extends Disposable implements IInputHandler {
     this._setCursor(0, 0);
     for (let yOffset = 0; yOffset < this._bufferService.rows; ++yOffset) {
       const row = buffer.y + buffer.ybase + yOffset;
-      buffer.lines.get(row).fill(cell);
-      buffer.lines.get(row).isWrapped = false;
+      const line = buffer.lines.get(row);
+      if (line) {
+        line.fill(cell);
+        line.isWrapped = false;
+      }
     }
     this._dirtyRowService.markAllDirty();
     this._setCursor(0, 0);
diff --git a/src/common/TestUtils.test.ts b/src/common/TestUtils.test.ts
index eacf92fe8..55e34084b 100644
--- a/src/common/TestUtils.test.ts
+++ b/src/common/TestUtils.test.ts
@@ -49,7 +49,6 @@ export class MockCharsetService implements ICharsetService {
   public serviceBrand: any;
   public charset: ICharset | undefined;
   public glevel: number = 0;
-  public charsets: ReadonlyArray<ICharset> = [];
   public reset(): void {}
   public setgLevel(g: number): void {}
   public setgCharset(g: number, charset: ICharset): void {}
diff --git a/src/common/Types.d.ts b/src/common/Types.d.ts
index cc7928c30..49a723b21 100644
--- a/src/common/Types.d.ts
+++ b/src/common/Types.d.ts
@@ -6,6 +6,7 @@
 import { ITerminalOptions as IPublicTerminalOptions } from 'xterm';
 import { IEvent, IEventEmitter } from 'common/EventEmitter';
 import { IDeleteEvent, IInsertEvent } from 'common/CircularList';
+import { IParams } from 'common/parser/Types';
 
 export interface IDisposable {
   dispose(): void;
@@ -300,3 +301,88 @@ export interface IWindowOptions {
   popTitle?: boolean;
   setWinLines?: boolean;
 }
+
+/**
+ * Calls the parser and handles actions generated by the parser.
+ */
+export interface IInputHandler {
+  onTitleChange: IEvent<string>;
+  onRequestScroll: IEvent<IAttributeData, boolean | void>;
+
+  parse(data: string | Uint8Array): void;
+  print(data: Uint32Array, start: number, end: number): void;
+
+  /** C0 BEL */ bell(): void;
+  /** C0 LF */ lineFeed(): void;
+  /** C0 CR */ carriageReturn(): void;
+  /** C0 BS */ backspace(): void;
+  /** C0 HT */ tab(): void;
+  /** C0 SO */ shiftOut(): void;
+  /** C0 SI */ shiftIn(): void;
+
+  /** CSI @ */ insertChars(params: IParams): void;
+  /** CSI SP @ */ scrollLeft(params: IParams): void;
+  /** CSI A */ cursorUp(params: IParams): void;
+  /** CSI SP A */ scrollRight(params: IParams): void;
+  /** CSI B */ cursorDown(params: IParams): void;
+  /** CSI C */ cursorForward(params: IParams): void;
+  /** CSI D */ cursorBackward(params: IParams): void;
+  /** CSI E */ cursorNextLine(params: IParams): void;
+  /** CSI F */ cursorPrecedingLine(params: IParams): void;
+  /** CSI G */ cursorCharAbsolute(params: IParams): void;
+  /** CSI H */ cursorPosition(params: IParams): void;
+  /** CSI I */ cursorForwardTab(params: IParams): void;
+  /** CSI J */ eraseInDisplay(params: IParams): void;
+  /** CSI K */ eraseInLine(params: IParams): void;
+  /** CSI L */ insertLines(params: IParams): void;
+  /** CSI M */ deleteLines(params: IParams): void;
+  /** CSI P */ deleteChars(params: IParams): void;
+  /** CSI S */ scrollUp(params: IParams): void;
+  /** CSI T */ scrollDown(params: IParams, collect?: string): void;
+  /** CSI X */ eraseChars(params: IParams): void;
+  /** CSI Z */ cursorBackwardTab(params: IParams): void;
+  /** CSI ` */ charPosAbsolute(params: IParams): void;
+  /** CSI a */ hPositionRelative(params: IParams): void;
+  /** CSI b */ repeatPrecedingCharacter(params: IParams): void;
+  /** CSI c */ sendDeviceAttributesPrimary(params: IParams): void;
+  /** CSI > c */ sendDeviceAttributesSecondary(params: IParams): void;
+  /** CSI d */ linePosAbsolute(params: IParams): void;
+  /** CSI e */ vPositionRelative(params: IParams): void;
+  /** CSI f */ hVPosition(params: IParams): void;
+  /** CSI g */ tabClear(params: IParams): void;
+  /** CSI h */ setMode(params: IParams, collect?: string): void;
+  /** CSI l */ resetMode(params: IParams, collect?: string): void;
+  /** CSI m */ charAttributes(params: IParams): void;
+  /** CSI n */ deviceStatus(params: IParams, collect?: string): void;
+  /** CSI p */ softReset(params: IParams, collect?: string): void;
+  /** CSI q */ setCursorStyle(params: IParams, collect?: string): void;
+  /** CSI r */ setScrollRegion(params: IParams, collect?: string): void;
+  /** CSI s */ saveCursor(params: IParams): void;
+  /** CSI u */ restoreCursor(params: IParams): void;
+  /** CSI ' } */ insertColumns(params: IParams): void;
+  /** CSI ' ~ */ deleteColumns(params: IParams): void;
+  /** OSC 0
+      OSC 2 */ setTitle(data: string): void;
+  /** ESC E */ nextLine(): void;
+  /** ESC = */ keypadApplicationMode(): void;
+  /** ESC > */ keypadNumericMode(): void;
+  /** ESC % G
+      ESC % @ */ selectDefaultCharset(): void;
+  /** ESC ( C
+      ESC ) C
+      ESC * C
+      ESC + C
+      ESC - C
+      ESC . C
+      ESC / C */ selectCharset(collectAndFlag: string): void;
+  /** ESC D */ index(): void;
+  /** ESC H */ tabSet(): void;
+  /** ESC M */ reverseIndex(): void;
+  /** ESC c */ fullReset(): void;
+  /** ESC n
+      ESC o
+      ESC |
+      ESC }
+      ESC ~ */ setgLevel(level: number): void;
+  /** ESC # 8 */ screenAlignmentPattern(): void;
+}
diff --git a/src/common/buffer/Buffer.ts b/src/common/buffer/Buffer.ts
index 152bab7a3..1de39dbd2 100644
--- a/src/common/buffer/Buffer.ts
+++ b/src/common/buffer/Buffer.ts
@@ -36,7 +36,7 @@ export class Buffer implements IBuffer {
   public savedY: number = 0;
   public savedX: number = 0;
   public savedCurAttrData = DEFAULT_ATTR_DATA.clone();
-  public savedCharset: ICharset | null = DEFAULT_CHARSET;
+  public savedCharset: ICharset | undefined = DEFAULT_CHARSET;
   public markers: Marker[] = [];
   private _nullCell: ICellData = CellData.fromCharData([0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE]);
   private _whitespaceCell: ICellData = CellData.fromCharData([0, WHITESPACE_CELL_CHAR, WHITESPACE_CELL_WIDTH, WHITESPACE_CELL_CODE]);
diff --git a/src/common/buffer/Types.d.ts b/src/common/buffer/Types.d.ts
index e229d69c3..c271f33c7 100644
--- a/src/common/buffer/Types.d.ts
+++ b/src/common/buffer/Types.d.ts
@@ -31,7 +31,7 @@ export interface IBuffer {
   hasScrollback: boolean;
   savedY: number;
   savedX: number;
-  savedCharset: ICharset | null;
+  savedCharset: ICharset | undefined;
   savedCurAttrData: IAttributeData;
   isCursorInViewport: boolean;
   markers: IMarker[];
diff --git a/src/common/data/Charsets.ts b/src/common/data/Charsets.ts
index 01087d8b1..c72d5a237 100644
--- a/src/common/data/Charsets.ts
+++ b/src/common/data/Charsets.ts
@@ -10,12 +10,12 @@ import { ICharset } from 'common/Types';
  * to be represented within the terminal with only 8-bit encoding. See ISO 2022
  * for a discussion on character sets. Only VT100 character sets are supported.
  */
-export const CHARSETS: { [key: string]: ICharset | null } = {};
+export const CHARSETS: { [key: string]: ICharset | undefined } = {};
 
 /**
  * The default character set, US.
  */
-export const DEFAULT_CHARSET: ICharset | null = CHARSETS['B'];
+export const DEFAULT_CHARSET: ICharset | undefined = CHARSETS['B'];
 
 /**
  * DEC Special Character and Line Drawing Set.
@@ -74,7 +74,7 @@ CHARSETS['A'] = {
  * United States character set
  * ESC (B
  */
-CHARSETS['B'] = null;
+CHARSETS['B'] = undefined;
 
 /**
  * Dutch character set
diff --git a/src/common/services/CharsetService.ts b/src/common/services/CharsetService.ts
index 47a015f6f..c5381065a 100644
--- a/src/common/services/CharsetService.ts
+++ b/src/common/services/CharsetService.ts
@@ -10,22 +10,23 @@ export class CharsetService implements ICharsetService {
   public serviceBrand: any;
 
   public charset: ICharset | undefined;
-  public charsets: ICharset[] = [];
   public glevel: number = 0;
 
+  private _charsets: (ICharset | undefined)[] = [];
+
   public reset(): void {
     this.charset = undefined;
-    this.charsets = [];
+    this._charsets = [];
     this.glevel = 0;
   }
 
   public setgLevel(g: number): void {
     this.glevel = g;
-    this.charset = this.charsets[g];
+    this.charset = this._charsets[g];
   }
 
-  public setgCharset(g: number, charset: ICharset): void {
-    this.charsets[g] = charset;
+  public setgCharset(g: number, charset: ICharset | undefined): void {
+    this._charsets[g] = charset;
     if (this.glevel === g) {
       this.charset = charset;
     }
diff --git a/src/common/services/Services.ts b/src/common/services/Services.ts
index 8fa3f57b3..6829d7b96 100644
--- a/src/common/services/Services.ts
+++ b/src/common/services/Services.ts
@@ -98,7 +98,6 @@ export interface ICharsetService {
 
   charset: ICharset | undefined;
   readonly glevel: number;
-  readonly charsets: ReadonlyArray<ICharset>;
 
   reset(): void;
 
@@ -113,7 +112,7 @@ export interface ICharsetService {
    * @param g
    * @param charset
    */
-  setgCharset(g: number, charset: ICharset): void;
+  setgCharset(g: number, charset: ICharset | undefined): void;
 }
 
 export const IDirtyRowService = createDecorator<IDirtyRowService>('DirtyRowService');