diff --git a/src/vs/editor/common/model/textModel.ts b/src/vs/editor/common/model/textModel.ts
index a4507e4baa29a5d5f3cba5b4c48de635612e98a6..53dc47f82e128b1f11e530e1c362cfc403127d03 100644
--- a/src/vs/editor/common/model/textModel.ts
+++ b/src/vs/editor/common/model/textModel.ts
@@ -898,6 +898,9 @@ export class TextModel extends Disposable implements model.ITextModel {
 	 * @param strict Do NOT allow a position inside a high-low surrogate pair
 	 */
 	private _isValidPosition(lineNumber: number, column: number, strict: boolean): boolean {
+		if (isNaN(lineNumber)) {
+			return false;
+		}
 
 		if (lineNumber < 1) {
 			return false;
@@ -908,6 +911,10 @@ export class TextModel extends Disposable implements model.ITextModel {
 			return false;
 		}
 
+		if (isNaN(column)) {
+			return false;
+		}
+
 		if (column < 1) {
 			return false;
 		}
@@ -933,8 +940,8 @@ export class TextModel extends Disposable implements model.ITextModel {
 	 * @param strict Do NOT allow a position inside a high-low surrogate pair
 	 */
 	private _validatePosition(_lineNumber: number, _column: number, strict: boolean): Position {
-		const lineNumber = Math.floor(typeof _lineNumber === 'number' ? _lineNumber : 1);
-		const column = Math.floor(typeof _column === 'number' ? _column : 1);
+		const lineNumber = Math.floor((typeof _lineNumber === 'number' && !isNaN(_lineNumber)) ? _lineNumber : 1);
+		const column = Math.floor((typeof _column === 'number' && !isNaN(_column)) ? _column : 1);
 		const lineCount = this._buffer.getLineCount();
 
 		if (lineNumber < 1) {
diff --git a/src/vs/editor/test/common/model/textModel.test.ts b/src/vs/editor/test/common/model/textModel.test.ts
index f507199793a2127658ce52fd4699df1db7bdfa46..d4506ec14e00f98a69c4fb5d4e94878f20f22488 100644
--- a/src/vs/editor/test/common/model/textModel.test.ts
+++ b/src/vs/editor/test/common/model/textModel.test.ts
@@ -620,6 +620,18 @@ suite('Editor Model - TextModel', () => {
 
 	});
 
+	test('validatePosition handle NaN.', () => {
+
+		let m = TextModel.createFromString('line one\nline two');
+
+		assert.deepEqual(m.validatePosition(new Position(NaN, 1)), new Position(1, 1));
+		assert.deepEqual(m.validatePosition(new Position(1, NaN)), new Position(1, 1));
+
+		assert.deepEqual(m.validatePosition(new Position(NaN, NaN)), new Position(1, 1));
+		assert.deepEqual(m.validatePosition(new Position(2, NaN)), new Position(2, 1));
+		assert.deepEqual(m.validatePosition(new Position(NaN, 3)), new Position(1, 3));
+	});
+
 	test('validateRange around high-low surrogate pairs 1', () => {
 
 		let m = TextModel.createFromString('a📚b');
@@ -829,6 +841,12 @@ suite('Editor Model - TextModel', () => {
 		assert.equal(model.getLineLastNonWhitespaceColumn(11), 0, '11');
 		assert.equal(model.getLineLastNonWhitespaceColumn(12), 0, '12');
 	});
+
+	test('#50471. getValueInRange with invalid range', () => {
+		let m = TextModel.createFromString('My First Line\r\nMy Second Line\r\nMy Third Line');
+		assert.equal(m.getValueInRange(new Range(1, NaN, 1, 3)), 'My');
+		assert.equal(m.getValueInRange(new Range(NaN, NaN, NaN, NaN)), '');
+	});
 });
 
 suite('TextModel.mightContainRTL', () => {