diff --git a/src/EscapeSequenceParser.ts b/src/EscapeSequenceParser.ts
index 7b336d06..c595976f 100644
--- a/src/EscapeSequenceParser.ts
+++ b/src/EscapeSequenceParser.ts
@@ -200,7 +200,6 @@ class DcsDummy implements IDcsHandler {
 export class EscapeSequenceParser implements IEscapeSequenceParser {
   public initialState: number;
   public currentState: number;
-  readonly transitions: TransitionTable;
 
   // buffers over several parse calls
   // FIXME: make those protected (needs workaround in tests)
@@ -227,10 +226,9 @@ export class EscapeSequenceParser implements IEscapeSequenceParser {
   protected _dcsHandlerFb: IDcsHandler;
   protected _errorHandlerFb: (state: IParsingState) => IParsingState;
 
-  constructor(transitions: TransitionTable = VT500_TRANSITION_TABLE) {
+  constructor(readonly transitions: TransitionTable = VT500_TRANSITION_TABLE) {
     this.initialState = ParserState.GROUND;
     this.currentState = this.initialState;
-    this.transitions = transitions;
     this.osc = '';
     this.params = [0];
     this.collect = '';
diff --git a/src/InputHandler.ts b/src/InputHandler.ts
index 4779435a..3bb61bd7 100644
--- a/src/InputHandler.ts
+++ b/src/InputHandler.ts
@@ -25,11 +25,12 @@ const GLEVEL = {'(': 0, ')': 1, '*': 2, '+': 3, '-': 1, '.': 2};
  * each function's header comment.
  */
 export class InputHandler implements IInputHandler {
-  private _parser: EscapeSequenceParser;
   private _surrogateHigh: string;
 
-  constructor(private _terminal: any) {
-    this._parser = new EscapeSequenceParser;  // FIXME: maybe as ctor argument
+  constructor(
+      private _terminal: any,
+      private _parser: EscapeSequenceParser = new EscapeSequenceParser)
+  {
     this._surrogateHigh = '';
 
     /**