diff --git a/src/BufferedTokenStream.ts b/src/BufferedTokenStream.ts
index 3f1ef2d4..f74011be 100644
--- a/src/BufferedTokenStream.ts
+++ b/src/BufferedTokenStream.ts
@@ -33,7 +33,7 @@ export class BufferedTokenStream implements TokenStream {
 	 * The {@link TokenSource} from which tokens for this stream are fetched.
 	 */
 	@NotNull
-	protected tokenSource: TokenSource;
+	private _tokenSource: TokenSource;
 
 	/**
 	 * A collection of all tokens fetched from the token source. The list is
@@ -75,11 +75,11 @@ export class BufferedTokenStream implements TokenStream {
 			throw new Error("tokenSource cannot be null");
 		}
 
-		this.tokenSource = tokenSource;
+		this._tokenSource = tokenSource;
 	}
 
 	@Override
-	getTokenSource(): TokenSource {
+	get tokenSource(): TokenSource {
 		return this.tokenSource;
 	}
 
@@ -295,8 +295,8 @@ export class BufferedTokenStream implements TokenStream {
 	}
 
 	/** Reset this token stream by setting its token source. */
-	setTokenSource(tokenSource: TokenSource): void {
-		this.tokenSource = tokenSource;
+	set tokenSource(tokenSource: TokenSource) {
+		this._tokenSource = tokenSource;
 		this.tokens.length = 0;
 		this.p = -1;
 	}
diff --git a/src/CommonToken.ts b/src/CommonToken.ts
index 8d033c98..28450519 100644
--- a/src/CommonToken.ts
+++ b/src/CommonToken.ts
@@ -114,7 +114,7 @@ export class CommonToken implements WritableToken {
 			result.source = oldToken.source;
 		} else {
 			result.text = oldToken.getText();
-			result.source = { source: oldToken.getTokenSource(), stream: oldToken.getInputStream() };
+			result.source = { source: oldToken.tokenSource, stream: oldToken.getInputStream() };
 		}
 
 		return result;
@@ -222,7 +222,7 @@ export class CommonToken implements WritableToken {
 	}
 
 	@Override
-	getTokenSource(): TokenSource | undefined {
+	get tokenSource(): TokenSource | undefined {
 		return this.source.source;
 	}
 
diff --git a/src/DefaultErrorStrategy.ts b/src/DefaultErrorStrategy.ts
index 93e32887..925e6adf 100644
--- a/src/DefaultErrorStrategy.ts
+++ b/src/DefaultErrorStrategy.ts
@@ -583,7 +583,7 @@ export class DefaultErrorStrategy implements ANTLRErrorStrategy {
 			current = lookback;
 		}
 
-		return this.constructToken(recognizer.getInputStream().getTokenSource(), expectedTokenType, tokenText, current);
+		return this.constructToken(recognizer.getInputStream().tokenSource, expectedTokenType, tokenText, current);
 	}
 
 	protected constructToken(
@@ -592,7 +592,7 @@ export class DefaultErrorStrategy implements ANTLRErrorStrategy {
 		tokenText: string,
 		current: Token): Token {
 		let factory: TokenFactory = tokenSource.getTokenFactory();
-		let x = current.getTokenSource();
+		let x = current.tokenSource;
 		let stream = x ? x.getInputStream() : undefined;
 
 		return factory.create(
diff --git a/src/Parser.ts b/src/Parser.ts
index 9d29f104..f206585f 100644
--- a/src/Parser.ts
+++ b/src/Parser.ts
@@ -386,7 +386,7 @@ export abstract class Parser extends Recognizer<Token, ParserATNSimulator> {
 	}
 
 	getTokenFactory(): TokenFactory {
-		return this._input.getTokenSource().getTokenFactory();
+		return this._input.tokenSource.getTokenFactory();
 	}
 
 	/**
@@ -436,7 +436,7 @@ export abstract class Parser extends Recognizer<Token, ParserATNSimulator> {
 	compileParseTreePattern(pattern: string, patternRuleIndex: number, lexer?: Lexer): ParseTreePattern {
 		if (!lexer) {
 			if (this.getInputStream()) {
-				let tokenSource = this.getInputStream().getTokenSource();
+				let tokenSource = this.getInputStream().tokenSource;
 				if (tokenSource instanceof Lexer) {
 					lexer = tokenSource;
 				}
diff --git a/src/ParserInterpreter.ts b/src/ParserInterpreter.ts
index a08909a3..6aff13ed 100644
--- a/src/ParserInterpreter.ts
+++ b/src/ParserInterpreter.ts
@@ -419,7 +419,7 @@ export class ParserInterpreter extends Parser {
 				throw new Error("Expected exception to have an offending token");
 			}
 
-			let source = tok.getTokenSource();
+			let source = tok.tokenSource;
 			let stream = source !== undefined ? source.getInputStream() : undefined;
 			let sourcePair = { source: source, stream: stream };
 
@@ -439,7 +439,7 @@ export class ParserInterpreter extends Parser {
 				this._ctx.addErrorNode(errToken);
 			}
 			else { // NoViableAlt
-				let source = tok.getTokenSource();
+				let source = tok.tokenSource;
 				let errToken: Token =
 					this.getTokenFactory().create(sourcePair,
 						Token.INVALID_TYPE, tok.getText(),
diff --git a/src/Token.ts b/src/Token.ts
index c6003b95..dd95aa9f 100644
--- a/src/Token.ts
+++ b/src/Token.ts
@@ -60,7 +60,7 @@ export interface Token {
 
 	/** Gets the {@link TokenSource} which created this token.
 	 */
-	getTokenSource(): TokenSource | undefined;
+	readonly tokenSource: TokenSource | undefined;
 
 	/**
 	 * Gets the {@link CharStream} from which this token was derived.
diff --git a/src/TokenStream.ts b/src/TokenStream.ts
index b704707f..dd7de6ca 100644
--- a/src/TokenStream.ts
+++ b/src/TokenStream.ts
@@ -65,7 +65,7 @@ export interface TokenStream extends IntStream {
 	 * stream.
 	 */
 	//@NotNull
-	getTokenSource(): TokenSource;
+	readonly tokenSource: TokenSource;
 
 	/**
 	 * Return the text of all tokens within the specified {@code interval}. This
diff --git a/src/UnbufferedTokenStream.tssoon b/src/UnbufferedTokenStream.tssoon
index f2287f93..6a1e5654 100644
--- a/src/UnbufferedTokenStream.tssoon
+++ b/src/UnbufferedTokenStream.tssoon
@@ -6,7 +6,7 @@
 // ConvertTo-TS run at 2016-10-04T11:26:58.9673509-07:00
 
 export class UnbufferedTokenStream implements TokenStream {
-	protected tokenSource: TokenSource; 
+	private _tokenSource: TokenSource; 
 
 	/**
 	 * A moving window buffer of the data being scanned. While there's a marker,
@@ -64,7 +64,7 @@ export class UnbufferedTokenStream implements TokenStream {
 	}
 
 	 constructor1(tokenSource: TokenSource, bufferSize: number)  {
-		this.tokenSource = tokenSource;
+		this._tokenSource = tokenSource;
 		this.tokens = new Token[bufferSize];
 		n = 0;
 		fill(1); // prime the pump
@@ -106,8 +106,8 @@ export class UnbufferedTokenStream implements TokenStream {
 	}
 
 	@Override
-	getTokenSource(): TokenSource {
-		return tokenSource;
+	get tokenSource(): TokenSource {
+		return this._tokenSource;
 	}
 
 	@NotNull
diff --git a/src/tree/pattern/RuleTagToken.ts b/src/tree/pattern/RuleTagToken.ts
index d1eeae9a..bfe313e0 100644
--- a/src/tree/pattern/RuleTagToken.ts
+++ b/src/tree/pattern/RuleTagToken.ts
@@ -164,7 +164,7 @@ export class RuleTagToken implements Token {
 	 * <p>The implementation for {@link RuleTagToken} always returns {@code null}.</p>
 	 */
 	@Override
-	getTokenSource(): TokenSource | undefined {
+	get tokenSource(): TokenSource | undefined {
 		return undefined;
 	}
 
diff --git a/test/tool/BaseTest.tssoon b/test/tool/BaseTest.tssoon
index 1d5479dc..5d89efda 100644
--- a/test/tool/BaseTest.tssoon
+++ b/test/tool/BaseTest.tssoon
@@ -1327,7 +1327,7 @@ export abstract class BaseTest {
 		}
 
 		@Override
-		getTokenSource(): TokenSource {
+		get tokenSource(): TokenSource {
 			return null;
 		}